Tag Archives: content

Content generation for passive frame consciousness

This is a continuation of posts on Morsella’s passive frame theory of consciousness.

Content is generated by modules that have input from bottom-up sensory paths, and from top-down paths. The generators are sensitive to context – a picture of a snake and a real snake are different. And they are unconscious – we cannot unsee a visual illusion even if we have knowledge of the real presentation.

The contents enter consciousness in an automatic manner. They are pushed in unconsciously not pulled in consciously – they just seem to happen, to ‘pop up’. The contents are under the control of unconscious associations – a word presented as a purely visual stimulus can be a phonetic representation in consciousness.

As well as sensory content generators, there are generators of action-related urges. Morsella uses the example: “when one holds one’s breath while underwater, or runs barefoot across the hot desert sand in order to reach water, one cannot help but consciously experience the inclinations to inhale or to avoid touching the hot sand, respectively. Regardless of the adaptiveness of the expressed actions, the conscious strife triggered by the external stimuli cannot be turned off voluntarily.

Thus the sensory presentation and the urges are generated in a way that is insulated or encapsulated from voluntary control. “Thus, although inclinations triggered by external stimuli can be behaviorally suppressed, they often cannot be mentally suppressed. One can think of many cases in which externally triggered conscious contents are more difficult to control than is overt behavior.

The contents of consciousness are independent of one another whether they are memories, stimuli from the environment are whatever, and this is adaptive. Cross contamination would interfere with successful behavior. The safer influence by context-sensitivity is unconscious, not the result of a conscious whim. This is an important point of difference with some other theories. “This view stands in contrast to several influential theoretical frameworks in which both the activation of, and nature of, conscious contents are influenced by what can be regarded as over-arching goals or current task demands. Because of the principle of encapsulation, conscious contents cannot influence each other either at the same time nor across time, which counters the everyday notion that one conscious thought can lead to another conscious thought. In the present framework, not only do contents not influence each other in the conscious field, but as Merker concludes, content generators cannot communicate the content they generate to another content generator. For example, the generator charged with generating the color orange cannot communicate ‘orange’ to any other content generator, for only this generator (a perceptual module) can, in a sense, understand and instantiate ‘orange.’ Hence, if the module charged with a particular content is compromised, that content is gone from the conscious field and no other module can ‘step in’ to supplant that content. As Merker notes, in constructing the conscious field, modules can send, not messages with content, but only ‘activation’ to each other. This activation, in turn, influences whether the receiver module will generate, not the kind of content generated by the module from which it received activation, but rather its own kind of content (e.g., a sound). Because messages of content cannot be transmitted to other content generators, the neural correlates of the content for X must include activation of the module that generates X, for a content cannot be segregated from the process by which it was engendered, as stated above.” Thus it seems that the contents of consciousness are not marshalled onto a stage or theatre but rather a network is formed connecting the original generators or modules.

The mosiac of independent content is discontinuous and arises in each conscious moment which quickly follow one another. What is watching this content? The passive frame theory says: “ “Importantly, the collective influence of the combination of contents in the conscious field is not toward the conscious field itself; instead … the conscious field is apprehended by the (unconscious) mechanisms comprising the skeletomotor output system. Thus, the conscious contents of blue, red, a smell, or the urge to blink are the tokens of a mysterious language understood, not by consciousness itself (nor by the physical world), but by the unconscious action mechanisms of skeletomotor output system. Why do things appear the way they do in the field? Because, in order to benefit action selection, they must differentiate themselves from all other tokens of the field—across various modalities/systems but within the same decision space.”

I have to add that this may indeed be the original evolutionary reason for consciousness and it may be the over-riding determinant of the mechanisms involved. However, it seems to me that having created a moment of consciousness the brain is loath to throw it away. It is somehow saved and used to form an episodic memory.

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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