More on the definition of consciousness

In my last post, I said that the phrase “subjective mental states”, used by Mark Conard, was without meaning. I did not explain why I find it meaningless, so I will now. You can read Conard’s review of my last post (here).

First, subjective – what can it mean? A thing, an event, a process or whatever, either exists or it doesn’t exist. And if it exists, it can be viewed in different ways. I can view something subjectively or objectively; how I view the something does not change what it is. And if I can view it subjectively then I most certainly can view it objectively, and vice versa. It makes absolutely no sense to say that something is solely subjective. As it happens consciousness can be viewed by introspection, it can also be viewed by inspecting the neural correlates of consciousness (NCC). Introspection does not make consciousness exclusively subjective and NCC do not make consciousness exclusively objective. I think we get a better, more useful view if we look objectively. You cannot say that the definition of consciousness is that it IS subjective. Subjectivity is in the mind of the beholder.

Second, mental – what does that mean? Mental as opposed to what? In this use it cannot mean just vaguely to do with thought. It must be taking the dualist meaning to do with mind as opposed to matter. I cannot deal in terms of magic-mind-matter, it is just meaningless.

And finally, state – what in this context can state mean? It implies that consciousness is a noun sort of thing rather than a verb sort of thing. If it is a state then it has to be somewhat static and be somewhere, but nothing in the brain seems static and in one place. We have to think of consciousness as a process and not a state.

I see consciousness as a process that is not yet clearly understood but involves the integration of a number of sources (sensory, motor/sensory prediction, emotion, volition) into a momentary perception of the world and our interaction within it. There are a number of events that are associated with this such as the synchronous two-way communication between the cortex and the thalamus, and the use of working memory. There may be many functions for consciousness, but one important one is to create experience to be stored in episodic memory. Our awareness of this moment of consciousness has the same basic form as our experience of a memory. Introspection seems to be the steering of attention on to the moment of consciousness and experiencing this as a sort of immediate memory. This way of looking at consciousness has the ring of truth about it, it is easy for me to live with.

But if consciousness has the definition of “subjective mental state” then as far as I am concerned it does not exist and I must find another name for the beautiful perceptions and emotions etc. that I experience. However, I have every right to use the word consciousness for the experiences I have and the ones others say they have, that sound to be very similar to mine. I do not accept that my consciousness is described by ‘subjective mental state’ and I insist that I have consciousness. And further I am not a freak of nature, I have a sane, working, experiencing brain.

 

What is consciousness?

Consciousness is a word that we can almost point at. When I say it I am fairly sure I don’t have to give a definition – I mean every one experiences consciousness and so they will know what I am talking about. But it is not so. As Inigo Montoya says, “You keep using that word. I do not think it means what you think it means”.

I read in a comment somewhere, long ago, that there were three ways to approach a physical explanation of consciousness: you could claim that as consciousness is not a physical thing, the explanation is impossible; or you could claim that it is physical but too mysterious to explain, the explanation is too hard; or you may claim that it is not what it appears to be and the explanation is obvious – it is not explained but explained away. It has been said that Dennett did this in his book Consciousness Explained – just explained it away.

As I said in a previous post (seeing past the trick) you cannot explain a magic trick as it appears but you can if you don’t believe the trick and look for the sleight of hand or the misdirection. If the subjective, non-physical, experience of a conscious mind is what has to be explained then that is a dead end and will remain a mystery. We have to give up our naïve sense of what consciousness is in order to understand it.

Michael Graziano did a piece in the NewYork Times Sunday Review (here) that portrays consciousness in a useful way.

… I believe a major change in our perspective on consciousness may be necessary, a shift from a credulous and egocentric viewpoint to a skeptical and slightly disconcerting one: namely, that we don’t actually have inner feelings in the way most of us think we do. …

How does the brain go beyond processing information to become subjectively aware of information? The answer is: It doesn’t. The brain has arrived at a conclusion that is not correct. When we introspect and seem to find that ghostly thing — awareness, consciousness, the way green looks or pain feels — our cognitive machinery is accessing internal models and those models are providing information that is wrong. The machinery is computing an elaborate story about a magical-seeming property. And there is no way for the brain to determine through introspection that the story is wrong, because introspection always accesses the same incorrect information. …

But the argument here is that there is no subjective impression; there is only information in a data-processing device. When we look at a red apple, the brain computes information about color. It also computes information about the self and about a (physically incoherent) property of subjective experience. The brain’s cognitive machinery accesses that interlinked information and derives several conclusions: There is a self, a me; there is a red thing nearby; there is such a thing as subjective experience; and I have an experience of that red thing. Cognition is captive to those internal models. Such a brain would inescapably conclude it has subjective experience. …

In the attention schema theory, attention is the physical phenomenon and awareness is the brain’s approximate, slightly incorrect model of it. In neuroscience, attention is a process of enhancing some signals at the expense of others. It’s a way of focusing resources. Attention: a real, mechanistic phenomenon that can be programmed into a computer chip. Awareness: a cartoonish reconstruction of attention that is as physically inaccurate as the brain’s internal model of color.

In this theory, awareness is not an illusion. It’s a caricature. Something — attention — really does exist, and awareness is a distorted accounting of it.”

I have picked out these bits of the argument but it is worth the time to read the original article. He (like philosophers Dennett, Churchland, Metzinger and others) is not explaining consciousness away but looking at what consciousness may actually be. Most scientists working on consciousness are also on this route – they are assuming that consciousness has a physical explanation, looking for evidence and, like Graziano, building theoretical models.

We cannot explain magic but we can explain why some things happen while appearing to be impossible. Look for what really happened and ignore what appeared to happen.

After writing this post but before posting it, I ran across a near perfect example of the problem. A philosopher called Mark Conard has a post called ‘When Science Gets Stupid’ (here). I doubt that he understood Graziano’s piece because he starts right out defining consciousness in exactly the form that it probably isn’t, “to be conscious is to be aware. It’s to have subjective mental states about one’s environment”. He does not refute Graziano’s argument but ignores it. Well, if you start with that as a firm definition, then you have already pre-judged the issue. You cannot explain scientifically ‘subjective mental states’ but possibly you can explain something that appears to be a subjective mental state. I have consciousness, personally, and I call it consciousness, but I very definitely do not feel I have subjective mental states. That is not the explanation I am looking for – I want an explanation of my consciousness not some other definition, subjective mental states, that seems meaningless. What on earth is a subjective mental state?

I found it offensive that Graziano was referred to as “a guy named Michael Graziano”. He is a very well respected scientist. Conrad also down grades Dennett and Churchland by implying that they are not somehow doing philosophy right (not with a capital P). “With it’s methods, science is wonderful, helpful, generates real knowledge about the world; but it’s incapable of investigating lived human experience in all its richness and meaningfulness. That isn’t to say, mind you, that there is no reasoned approach to human experience, no arguments to be made, no evidence to examine. It’s only to say that we need a different methodology–that of Philosophy!”As I had never encountered Conrad before, his pulling rank does not impress me. And his arguments just miss the point entirely. “You keep using that word. I do not think it means what you think it means”.

Remembering visual images

There is an interesting recent paper (see citation) on visual memory. The researchers’ intent is to map and areas and causal directions between them for a particular process in healthy individuals so that sufferers showing lost of that process can be studied in the same way and the areas/connections which are faulty identified. In this study they were looking at encoding of vision for memory.

40 healthy subjects were examined. “… participants were presented with stimuli that represented a balanced mixture of indoor (50%) and outdoor (50%) scenes that included both images of inanimate objects as well as pictures of people and faces with neutral expressions. Attention to the task was monitored by asking participants to indicate whether the scene was indoor or outdoor using a button

box held in the right hand. Participants were also instructed to memorize all scenes for later memory testing. During the control condition, participants viewed pairs of scrambled images and were asked to indicate using the same button box whether both images in each pair were the same or not (50% of pairs contained the same images). Use of the control condition allowed for subtraction of visuo-perceptual, decision-making, and motor aspects of the task, with a goal of improved isolation of the memory encoding aspect of the active condition.” All the subjects performed well on both tasks and on later recognition of the scene they were asked to remember. “Thirty-two ICA components were identified. Of these, 10 were determined to be task-related (i.e., not representing noise or components related to the control condition) and were included in further analyses and model generation. Each retained component was attributed to a particular network based on previously published data. ” Granger causality analysis was carried out on each pair of the 10 components.

Here is the resulting picture:visual plan

The authors give a description of the many functions that have been attributed to their 10 areas (independent components) which is interesting reading. But not very significant because the areas are on the large size and because it is reasonable to argue from a specific function to an active area but not from an active area to a specific function. The information does have a bearing on some theories and models. The fact that this work does not itself produce a model does not make it less useful in studying abnormal visual memory encoding.

The involvement of the ‘what’ visual stream rather than the stream used for motor actions is expected, as is the involvement of working memory. There is clearly a major importance of attention in this process. The involvement of language/concepts is interesting. “Episodic memory is defined as the ability to consciously recall dated information and spatiotemporal relations from previous experiences, while semantic memory consists of stored information about features and attributes that define concepts. The visual encoding of a scene in order to remember and recognize it later (i.e., visual memory encoding) engages both episodic and semantic memory, and an efficient retrieval system is needed for later recall.” The data is likely to be useful in evaluating theoretical ideas. The author mention support for the hemispheric encoding/retrieval asymmetry model.

The abstract:

Memory encoding engages multiple concurrent and sequential processes. While the individual processes involved in successful encoding have been examined in many studies, a sequence of events and the importance of modules associated with memory encoding has not been established. For this reason, we sought to perform a comprehensive examination of the network for memory encoding using data driven methods and to determine the directionality of the information flow in order to build a viable model of visual memory encoding. Forty healthy controls ages 19–59 performed a visual scene encoding task. FMRI data were preprocessed using SPM8 and then processed using independent component analysis (ICA) with the reliability of the identified components confirmed using ICASSO as implemented in GIFT. The directionality of the information flow was examined using Granger causality analyses (GCA). All participants performed the fMRI task well above the chance level (.90% correct on both active and control conditions) and the post-fMRI testing recall revealed correct memory encoding at 86.3365.83%. ICA identified involvement of components of five different networks in the process of memory encoding, and the GCA allowed for the directionality of the information flow to be assessed, from visual cortex via ventral stream to the attention network and then to the default mode network (DMN). Two additional networks involved in this process were the cerebellar and the auditory-insular network. This study provides evidence that successful visual memory encoding is dependent on multiple modules that are part of other networks that are only indirectly related to the main process. This model may help to identify the node(s) of the network that are affected by a specific disease processes and explain the presence of memory encoding difficulties in patients in whom focal or global network dysfunction exists. ”
ResearchBlogging.org

Nenert, R., Allendorfer, J., & Szaflarski, J. (2014). A Model for Visual Memory Encoding PLoS ONE, 9 (10) DOI: 10.1371/journal.pone.0107761

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Another new neuron type

 

In a press release (here) about a Neuron Journal paper (see citation below), it was announced that there were neurons in the hippocampus with a newly discovered anatomy, in fact they are common there.

The model of a neuron is that it has a cell body with branches (dendrites) in one area that receive input from other neurons and a long extension (axon) that has branches at its end to output signals to other neurons. The standard picture is that there is a complex summation of synaptic inputs on the dendrite branches and then a summation on the body of the cell of the dendrites which either reaches the threshold for firing or not. If threshold is reached the activity travels down the axon to the synapses with other neurons.

The newly discovered neurons have a bypass, shunt or privileged path. The axon in these cells does not start on the cell body but on a dendrite that is on the axon side of the cell body. Therefore input to this particular dendrite does not have to pass though the cell body but can directly send signals down the axon. This axon can fire if the dendrite it is attached to reaches threshold or if the cell body reaches threshold due to activity on the other dendrites.

A metaphor might be like this. The decision whether or not to fire is taken by small committees with pro and con members, then the results of those committees goes to a higher committee. If that committee decides to fire then firing will happen. On the other hand, the boss and his advisors can just walk in and order fire if they choose.

These pyramid cells in the hippocampus would have an important role in memory. What the function of this arrangement is has not yet been researched.

Here is the abstract:

Neuronal processing is classically conceptualized as dendritic input, somatic integration, and axonal output. The axon initial segment, the proposed site of action potential generation, usually emanates directly from the soma. However, we found that axons of hippocampal pyramidal cells frequently derive from a basal dendrite rather than from the soma. This morphology is particularly enriched in central CA1, the principal hippocampal output area. Multiphoton glutamate uncaging revealed that input onto the axon-carrying dendrites (AcDs) was more efficient in eliciting action potential output than input onto regular basal dendrites. First, synaptic input onto AcDs generates action potentials with lower activation thresholds compared with regular dendrites. Second, AcDs are intrinsically more excitable, generating dendritic spikes with higher probability and greater strength. Thus, axon-carrying dendrites constitute a privileged channel for excitatory synaptic input in a subset of cortical pyramidal cells.

Citation: C. Thome, T. Kelly, A. Yanez, C. Schultz, M. Engelhardt, S. B. Camebridge, M. Both, A. Draguhn, H. Beck and A. V. Egorov (2014): Axon-Carrying Dendrites Convey Privileged Synaptic Input in Hippocampal Neurons. Neuron, 83, 1418-1430.

Fine control

My last blog on timing in some neurons in the cerebellum has started a string of thoughts. Here we have a part of the brain with an anatomy that is well mapped as opposed to many other parts. It has more neurons than the rest of the brain put together. It has grown relatively larger in human evolution then any other part of the brain. There are theories about how the system works, and yet, its actions are not understood in detail and new information on one of its important cell types was a surprise. (previous blog)

Abstract (Barton see citation below):

Humans’ unique cognitive abilities are usually attributed to a greatly expanded neocortex, which has been described as “the crowning achievement of evolution and the biological substrate of human mental prowess”. The human cerebellum, however, contains four times more neurons than the neocortex and is attracting increasing attention for its wide range of cognitive functions. Using a method for detecting evolutionary rate changes along the branches of phylogenetic trees, we show that the cerebellum underwent rapid size increase throughout the evolution of apes, including humans, expanding significantly faster than predicted by the change in neocortex size. As a result, humans and other apes deviated significantly from the general evolutionary trend for neocortex and cerebellum to change in tandem, having significantly larger cerebella relative to neocortex size than other anthropoid primates. These results suggest that cerebellar specialization was a far more important component of human brain evolution than hitherto recognized and that technical intelligence was likely to have been at least as important as social intelligence in human cognitive evolution. Given the role of the cerebellum in sensory-motor control and in learning complex action sequences, cerebellar specialization is likely to have underpinned the evolution of humans’ advanced technological capacities, which in turn may have been a preadaptation for language.

This enlargement has been in the neocerebellum which is not primarily concerned with the fine tuning of movements of the whole body and limbs. What appears to have increased is: the ability to learn by being taught, imitating and practice; fine control of the hands as is needed for tool making; find control of the larynx as is needed for speaking; and it might said, fine control of any sequential process including language and some types of thought.

Wikipedia gives a summary of the neocerebral connections. “The lateral zone, which in humans is by far the largest part, constitutes the cerebrocerebellum, also known as neocerebellum. It receives input exclusively from the cerebral cortex (especially the parietal lobe) via the pontine nuclei (forming cortico-ponto-cerebellar pathways), and sends output mainly to the ventrolateral thalamus (in turn connected to motor areas of the premotor cortex and primary motor area of the cerebral cortex) and to the red nucleus. There is disagreement about the best way to describe the functions of the lateral cerebellum: it is thought to be involved in planning movement that is about to occur, in evaluating sensory information for action, and in a number of purely cognitive functions as well, such as determining the verb which best fits with a certain noun (as in “sit” for “chair”).

A computing mechanism for fine control of a process using feedback from the environment has an almost universal usefulness. It does not initiate but controls an action. It evolved to give us balance and posture, to smooth our actions and make them more accurate, to move the eyes and give us a stationary vision from moving eyes, and to steer the eyes to points of attention. What we appear to have gained is extremely fine control of some muscles and the ability to use the same mechanisms for language, music and other forms of thought and social communication. It appears essential to supervised learning. And here is a biggy – it may be responsible for knitting together the fragments of memory and knowledge that produces imagination.
ResearchBlogging.org

Barton, R., & Venditti, C. (2014). Rapid Evolution of the Cerebellum in Humans and Other Great Apes Current Biology DOI: 10.1016/j.cub.2014.08.056

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A new feature of neurons

There are articles asking, “Are we ever going to understand the brain?” They imply that we have been studying the brain for long enough to be able to say how it works, if we are ever going to, and therefore hinting that it is a permanent mystery. But every week or so some new wrinkle on the brain’s nature comes to light. The brain is far more complicated and far less understood than many think.

Recently a paper appeared that pointed to a wholly new feature of neurons. (citation below) Johansson and his colleagues demonstrate a surprising feature of at least some neurons. They looked at a well known response. When a puff of air is directed at the eye, there is a blink. If this is done over and over with the same time interval between a signal and the puff, a reflex is formed so that the blink happens at just the right time to protect the eye from the puff. This is a standard conditioned reflex and we thought we understood conditioned reflexes. The researchers found that the learning of the time between signal and puff was not a function of a network of cells but an internal function of one type of cell. “The data strongly suggest that the main timing mechanism is within the Purkinje cell and that its nature is cellular rather than a network property. Parallel fiber input lacking any temporal pattern can elicit Purkinje cell responses timed to intervals at least as long as 300 ms. … In addition, the data show that a main part of the timing of the conditioned response relies on intrinsic cellular mechanisms rather than on a temporal pattern in the input signal. ” We have been modeling neurons as firing, or not, as a result of the strength of the signals at their synapses; and firing, if they do, immediately. Any timing effects were assumed to be produced by network structures. Neurons were modeled as very fancy switches but with no timing capabilities. Now understanding has changed. Large changes in understanding, like this one, happen regularly. We are a long way from understanding the mechanisms in the brain.

Here is the Significance and Abstract:

The standard view of neural signaling is that a neuron can influence its target cell by exciting or inhibiting it. An important aspect of the standard view is that learning consists of changing the efficacy of synapses, either strengthening (long-term potentiation) or weakening (long-term depression) them. In studying how cerebellar Purkinje cells change their responsiveness to a stimulus during learning of conditioned responses, we have found that these cells can learn the temporal relationship between two paired stimuli. The cells learn to respond at a particular time that reflects the time between the stimuli. This finding radically changes current views of both neural signaling and learning.

The standard view of the mechanisms underlying learning is that they involve strengthening or weakening synaptic connections. Learned response timing is thought to combine such plasticity with temporally patterned inputs to the neuron. We show here that a cerebellar Purkinje cell in a ferret can learn to respond to a specific input with a temporal pattern of activity consisting of temporally specific increases and decreases in firing over hundreds of milliseconds without a temporally patterned input. Training Purkinje cells with direct stimulation of immediate afferents, the parallel fibers, and pharmacological blocking of interneurons shows that the timing mechanism is intrinsic to the cell itself. Purkinje cells can learn to respond not only with increased or decreased firing but also with an adaptively timed activity pattern.
ResearchBlogging.org

Johansson, F., Jirenhed, D., Rasmussen, A., Zucca, R., & Hesslow, G. (2014). Memory trace and timing mechanism localized to cerebellar Purkinje cells Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1415371111

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Down with untrue intros

 

There are often opening sentences like, “only humans can x” or “only primates can x”. Why do people assume these sorts of statements are true without checking? Why does no one seem to complain? Either authors and readers don’t really care if the statements are true – they are just openers and not the important part of the piece; or they want the statements to be true and so are shy about looking at any evidence.

A recent paper (Anna Kis, Ludwig Huber, Anna Wilkinson. Social learning by imitation in a reptile (Pogona vitticeps). Animal Cognition, 2014) was reported in ScienceDaily with the opening line, “The ability to acquire new skills through the ‘true imitation’ of others’ behaviour is thought to be unique to humans and advanced primates, such as chimpanzees.” I knew this was not true and that other animals have this skill (a number of mammals besides primates and a number of birds). Looking at the abstract of the paper, I found a similar opening line. It was not so restrictive – “The ability to learn through imitation is thought to be the basis of cultural transmission and was long considered a distinctive characteristic of humans. There is now evidence that both mammals and birds are capable of imitation.” But even this is a bit restricted as octopuses also learn from one another. We should not be sure that some animal (an social insect for example) does not do x unless we have looked to see. And throw-away openings should be at least true.

But the paper has interesting news. Bearded dragons can learn from one another! Reptiles can be included too. We are more closely related to these reptiles than to birds. This finding strengthens the idea that social learning is an ancient skill in vertebrates, rather than separately evolved in various types of vertebrates. Although it is still reasonable to think that it evolved separately in invertebrates.

Here is the abstract:

The ability to learn through imitation is thought to be the basis of cultural transmission and was long considered a distinctive characteristic of humans. There is now evidence that both mammals and birds are capable of imitation. However, nothing is known about these abilities in the third amniotic class—reptiles. Here, we use a bidirectional control procedure to show that a reptile species, the bearded dragon (Pogona vitticeps), is capable of social learning that cannot be explained by simple mechanisms such as local enhancement or goal emulation. Subjects in the experimental group opened a trap door to the side that had been demonstrated, while subjects in the ghost control group, who observed the door move without the intervention of a conspecific, were unsuccessful. This, together with differences in behaviour between experimental and control groups, provides compelling evidence that reptiles possess cognitive abilities that are comparable to those observed in mammals and birds and suggests that learning by imitation is likely to be based on ancient mechanisms.

Conscious content

I have been thinking about some information in a not too recent paper. (see citation below) Panagiotaropoulos and others looked at the location of the content of consciousness in primates. They used binocular flash suppression (BFS) to give two different visual stimulation that compete for a place in the content of consciousness. Here is their figure and description of the method:

fig1We recorded simultaneously neuronal discharges and LFPs (local field potentials) in the LPFC (lateral prefrontal cortex) of two alert macaques during a passive fixation task that included randomly interleaved trials of physical alternation and BFS. BFS constitutes a highly controlled variant of BR (binocular rivalry) that has been extensively used to dissociate subjective visual perception from purely sensory stimulation. The BFS (‘‘perceptual’’) trials, as well as the physical (‘‘sensory’’) alternation of the visual stimuli that was used as a control condition, are depicted in Figure 1. Every trial starts with the presentation of a fixation spot in both eyes that is binocularly fused and remains on until the end of the trial. In both sensory (Figure 1A, upper panel, ‘‘Physical alternation’’) and perceptual (Figure 1A, lower panel, ‘‘Flash suppression’’) trials, a fixation spot was presented for 300 ms followed by monocular stimulation with the same visual pattern (a polar checkerboard in the paradigm presented in the figure). In perceptual trials, 1 s after stimulus onset, a disparate visual pattern (here, a monkey face) is suddenly flashed to the corresponding part of the contralateral eye. It has been repeatedly shown that, in both humans and monkeys, the flashed stimulus remains dominant for at least 1,000 ms, robustly suppressing the perception of the contralaterally presented visual pattern that is still physically present. … Thus, in perceptual trials, a visual competition period dissociating sensory stimulation from perception is externally induced for at least 1,000 ms. During this period, the newly presented image is perceptually dominant while the initially presented visual pattern is perceptually suppressed despite its physical presence in the retina (Figure 1A, middle panel). In sensory trials, the same visual patterns physically alternate between the two eyes, resulting in a visual percept identical to the perceptual condition but this time without any concurrent visual competition (Figure 1A, upper panel). Specifically, after 1 s of visual stimulation, the initially presented pattern is removed and immediately followed by the presentation of the disparate pattern in the contralateral eye.

Under this methodology it is possible to tell whether the neurons are registering the information that is actually on the retina or the information that is actually in consciousness, when they differ. Previous research has established that conscious content is not necessarily found in the visual system up to the completion of perception. The temporal lobe is the first place where the content of consciousness alone is registered in an area with a two-way communication with the lateral prefrontal cortex and that is why the researchers looked for the conscious signal in the LPFC (and we indeed found it). These two areas, as well as their direct connections, are each connected to a particular part of the thalamus, the pulvinar nucleus. This traffic seems to carry the mark of consciousness in the high frequency of the brain waves.

It is very interesting to see that the visual perception is complete and the ambiguities resolved for both the image that is conscious and the one that is unconscious before the temporal – prefrontal – thalamus signals show the content that is destined for awareness. There does not appear to be a difference between the processing of conscious and unconscious input up to the point of entering the consciousness loops. There are not two minds creating two perceptions, but one mind producing both perceptions, only one of which becomes conscious. The process of perception completes without, it appears, being affected by the mechanism of conscious awareness in any substantial way.

Here is the abstract:

Neuronal discharges in the primate temporal lobe, but not in the striate and extrastriate cortex, reliably reflect stimulus awareness. However, it is not clear whether visual consciousness should be uniquely localized in the temporal association cortex. Here we used binocular flash suppression to investigate whether visual awareness is also explicitly reflected in feature-selective neural activity of the macaque lateral prefrontal cortex (LPFC), a cortical area reciprocally connected to the temporal lobe. We show that neuronal discharges in the majority of single units and recording sites in the LPFC follow the phenomenal perception of a preferred stimulus. Furthermore, visual awareness is reliably reflected in the power modulation of high-frequency (>50Hz) local field potentials in sites where spiking activity is found to be perceptually modulated. Our results suggest that the activity of neuronal populations in at least two association cortical areas represents the content of conscious visual perception.

ResearchBlogging.org

Panagiotaropoulos, T., Deco, G., Kapoor, V., & Logothetis, N. (2012). Neuronal Discharges and Gamma Oscillations Explicitly Reflect Visual Consciousness in the Lateral Prefrontal Cortex Neuron, 74 (5), 924-935 DOI: 10.1016/j.neuron.2012.04.013

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Sometimes choices are not thought out

In some competitive situations animals can produce random behavior rather than behavior based on prior experience. The anterior cingulate cortex is where strategies based on models of reality and history are generated; switching to random behavior is done by inputs to this part of the brain from the locus coeruleus. This was reported in a recent paper (citation below).

We generally assume that deciding what to do is based on the best guess of what will be the successful thing to do. Why would random behavior ever be better? It would be if the world seemed to change from what it had been and a new model needed to be constructed. Random exploration would be helpful. Or, there is the case of an opponent that is better at the fight. “We find that when faced with a competitor that they cannot defeat by counterprediction, animals switch to a distinct mode of action selection consistent with stochastic choice. In this mode, characterized by highly variable choice sequences, behavior becomes dramatically less dependent on the history of outcomes associated with different actions and becomes independent from the ACC. ” Primates appear to always try counterprediction before using random choice.

The random behaviour is not the product of the ACC system but is generated elsewhere. A mixture of modelling in the ACC and a random overlay seems the normal state with the amount of randomness depending on the confidence in the modelling. It is like a balance between exploitation and exploration set by the performance of the ACC model. “We note that complete abandonment of an internal model and adoption of a fully stochastic behavioral mode is normally maladaptive because of the associated insensitivity to new information. In rats, such a mode appears to be triggered when repeated modeling efforts prove to be ineffective and thus bears a similarity to the condition of learned helplessness thought to follow the sustained experience of the futility of one’s actions. Intriguingly, functional imaging studies in humans have suggested that a chronic reduction in ACC activity might play a role in this disorder .

This arrangement also seems to fit with the ‘deliberate’ errors that happen in well-learned sequences in sports, bird song, and children’s speech. Confidence in the model is occasionally tested.

Here is the abstract:

Behavioral choices that ignore prior experience promote exploration and unpredictability but are seemingly at odds with the brain’s tendency to use experience to optimize behavioral choice. Indeed, when faced with virtual competitors, primates resort to strategic counterprediction rather than to stochastic choice. Here, we show that rats also use history- and model-based strategies when faced with similar competitors but can switch to a “stochastic” mode when challenged with a competitor that they cannot defeat by counterprediction. In this mode, outcomes associated with an animal’s actions are ignored, and normal engagement of anterior cingulate cortex (ACC) is suppressed. Using circuit perturbations in transgenic rats, we demonstrate that switching between strategic and stochastic behavioral modes is controlled by locus coeruleus input into ACC. Our findings suggest that, under conditions of uncertainty about environmental rules, changes in noradrenergic input alter ACC output and prevent erroneous beliefs from guiding decisions, thus enabling behavioral variation.
ResearchBlogging.org

Tervo, D., Proskurin, M., Manakov, M., Kabra, M., Vollmer, A., Branson, K., & Karpova, A. (2014). Behavioral Variability through Stochastic Choice and Its Gating by Anterior Cingulate Cortex Cell, 159 (1), 21-32 DOI: 10.1016/j.cell.2014.08.037

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Doing a task while asleep

A recent paper (citation below) describes subjects working away at a task, categorizing words, while asleep. Here is the abstract:

Falling asleep leads to a loss of sensory awareness and to the inability to interact with the environment. While this was traditionally thought as a consequence of the brain shutting down to external inputs, it is now acknowledged that incoming stimuli can still be processed, at least to some extent, during sleep. For instance, sleeping participants can create novel sensory associations between tones and odors or reactivate existing semantic associations, as evidenced by event-related potentials. Yet, the extent to which the brain continues to process external stimuli remains largely unknown. In particular, it remains unclear whether sensory information can be processed in a flexible and task-dependent manner by the sleeping brain, all the way up to the preparation of relevant actions. Here, using semantic categorization and lexical decision tasks, we studied task-relevant responses triggered by spoken stimuli in the sleeping brain. Awake participants classified words as either animals or objects (experiment 1) or as either words or pseudowords (experiment 2) by pressing a button with their right or left hand, while transitioning toward sleep. The lateralized readiness potential (LRP), an electrophysiological index of response preparation, revealed that task-specific preparatory responses are preserved during sleep. These findings demonstrate that despite the absence of awareness and behavioral responsiveness, sleepers can still extract task- relevant information from external stimuli and covertly prepare for appropriate motor responses.

This study does not address whether a task can be initiated while asleep because the subjects fell asleep while engaged in the task. And, of course, as movement is blocked during REM sleep, the initiation of movement while unconscious was also not tested. What was tested was the processing required to carry on the task and prepare for movement.

Some previous postings have looked at unconscious processes. Some experiments used unconscious priming to test whether such priming can result in particular processes. In (does control of cognition have to be conscious?) it was indicated that control of cognition (conflict adaption) can be unconscious and in (unconscious effects) it was shown that unconscious priming could be responsible for perceiving, doing semantic operations and making decisions. Other experiments have used control over the use of consciousness by forcing its content. In (discovering rules unconsciously) blocking the use of consciousness for a particular problem showed that unconscious processing was superior to conscious processing for discovering ‘grammatical’ rules. Now we have a third method, the comparison between awake and asleep states showing that task-related processing can proceed unconsciously, starting from perception, through processing and decision making to preparation of motor responses.

It is not news any more that most of the processes in the brain can be done unconsciously. We are not aware of these processes, naturally, because they are unconscious, but that does not mean they do not happen. The bulk of the brain’s activity is unconscious. We should not be surprised at unconscious thought. The exceptions that, to date, appear to require consciousness are the formation of explicit memories, the use of working memory, and the particular form of awareness that we associate with consciousness. Perhaps consciousness has more to due with a particular use of memory rather than a particular type of thought process.
ResearchBlogging.org

Kouider, S., Andrillon, T., Barbosa, L., Goupil, L., & Bekinschtein, T. (2014). Inducing Task-Relevant Responses to Speech in the Sleeping Brain Current Biology, 24 (18), 2208-2214 DOI: 10.1016/j.cub.2014.08.016

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