What follows is the text for the poster that I presented at the 2013 conference for the Association for the Scientific Study of Consciousness, ASSC 17, July 12th-15th.
Abstract
Reciprocal interactions between
bottom-up sensory areas and top-down association areas maintain, discard, and
transform information resulting in the orchestration of imagery generation and
internally guided thought. Representations are temporarily maintained in
association areas and utilized as imagery specifications that are fed back into
lower-order sensory areas where they are continually used in the construction
of successive topographic maps. Salient features from these transient, sensory
maps progress up the cortical hierarchy where they activate the corresponding
representations in association cortex, adding them to the store of temporarily
maintained features. Thus, the most salient, novel, or goal-relevant features
from the last several mappings are maintained in association areas. The fact
that some representations within association areas remain active for prolonged
periods, over the duration of several reciprocal top-down to bottom-up
transformations, is taken to account for the continuity found between
successive topographic maps. The sustained and dynamically overlapping activity
of higher-order association nodes allows consecutive topographic maps to: have
related content, exhibit progressive qualities, implement learned algorithms,
and carry thematic or narrative continuity over sequential processing states.
Introduction
The general intention of the
present work is to delineate a multistep neurological process suggested to be
responsible for mental continuity and internally generated thought. The work
considers how sustained neural firing of nodes in association cortex underlies
the uninterrupted persistence of goal-relevant fragments of long term memory
(LTM), allowing an interrelated sequence of brain states.
When mammals process information,
they match perceptual stimuli with preexisting, invariant, template-like
representations held in memory. These representations are composed of groups of
highly connected cortical neurons that can be repeatedly used to represent the
most frequently associated features of a common, reoccuring event or stimulus. These ensembles
are suggested to be composed of large groups of neurons that have been bound
due to simultaneous activity in the past. When multiple representations are coactivated the individual elements spread and
pool their activation energy resulting in the selection of representations for
continued activation, deactivation and new activation. This process is
suggested to select the content for the stream of thought.
FIG.1
is a diagram illustrating the ways in which high-level features are displaced,
maintained, and newly activated in the brain to form a “stream” or “train” of
thought. Each representation is represented by a letter. 1) Shows that feature
A has already been deactivated and that B, C, D and E are now coactivated.
When coactivated,
these features spread and pool their activation energy, resulting in the
convergence of activity onto a new feature, F. Once F becomes active, it
immediately becomes a coactivate, restarting the cycle. 2) Shows that
feature B has been deactivated while C, D, E and F are coactivated
and G is newly activated.
Neurological
Continuity
Activity
from active representations fluctuates back and forth between early, bottom-up
sensory cortex (where activity is metric, topographic and transient) and late,
top-down association cortex (where activity is abstract, conceptual and
persistent). Currently active representations in association areas spread their
unique constellation of activity backwards through the structurally descriptive
hierarchy towards sensory areas, where they are used to guide the construction
of composite topographical maps. Sensory areas and association areas
continually stimulate each other into building interpretations of the other’s
outputs resulting in a continual conversational interchange.
The
fact that some ensembles within association areas remain active for prolonged
periods, over the duration of several reciprocal top-down to bottom-up
communications, is taken to account for instances of continuity found between
successive topographic maps. This feature of continued activation augments
associative searches by allowing specific representations to be used as
function parameters for more than one cycle. The longer ensembles in
association areas can be continuously activated - over a series of states - the
longer they can influence sequences of sensory imagery in a sustained and
consistent way allowing continuous, progressive alterations to the imagery. The
result is a stream of consciousness where each thought is quantitatively
different from preceding thoughts, as newly relevant representations are added
and the least relevant ones are removed.
FIG 2. is a diagram depicting the
reciprocal transformations of information between lower-order sensory nodes and
higher-order PFC nodes. Sensory areas can only create one sensory image at a
time, whereas the PFC is capable of holding the salient or goal-relevant
features of several sequential images at the same time.
Mental
Continuity
The
pattern of activity in the brain is constantly changing, but because some
individual neurons exhibit sustained firing during these changes, particular
features of the overall pattern will be continuous, uninterrupted, or conserved
over time. The most enduringly active PFC nodes correspond to what the
individual is most focused on, the underlying theme or element that stays the
same as other contextual features fluctuate. If it were not for the phenomenon
of sustained firing, information could not be carried over to subsequent
states, and the ability to process or make associations between temporally
distant stimuli would be disrupted. This may be why the prefrontal cortex is
associated with working memory, executive function, mental modeling, planning,
and goal setting. This may also explain why agents without the analogue of a
PFC, such as most life forms and current artificial intelligence, do not
exhibit human-like higher-order thinking.
Where
does this process initiate? Perhaps there is no objective stopping or starting
point of thought. Instead, thought itself may be composed of the startings and stoppings of huge numbers of
individual elements that exhibit staggered and overlapping activity (Reser, 2012, 2013). In the most intelligent
animals, thoughts are composed of larger sets of elements that are capable of
remaining coactivated longer allowing motor output and
sensory activity to reflect several seconds of overlapping association
activity.
FIG.
3 shows that representations B, C, D, and E, which are held active in the PFC,
all spread their activation energy to lower-order sensory areas where a
composite image is built that is based on prior experience with these features.
2) Shows that features involved in the retinotopic imagery from time sequence 1 converge on
the PFC neurons responsible for feature F. Feature B drops out of activation,
and C, D, E and F remain active and diverge back onto visual cortex, mirroring
the pattern of activity shown in Figure 1.
Conclusions
Mammals most likely evolved the capacity
to use the DA/PFC system to sustain certain representations so that important
groupings of representations could be interrogated and modeled. The PFC
representations of rewarding, punishing, salient, uncertain, or unpredicted
events are kept active over time to aid in the processing of their
significance. It is highly probable that sequences of lower-order topographic
images depict and explore hypothetical relationships between higher-order,
top-down representations. Because these features remain active, they can be
used repeatedly as specifications that guide the generation of mental imagery
in sensory areas. The continuity causes each new topographic map to be embedded
in the previous one, creating a cyclical, nested flow of information
processing. This amounts to a continual attempt to search sensory memory for a
topographic image that can meaningfully incorporate the important features.
The
feature that is referred to here as mental continuity may be a major facet of
the general factor of intelligence and may exhibit individual differences in
humans where severe deficits in this capacity may map onto various clinical
syndromes, such as: psychosis, schizophrenia, mental retardation, cognitive
aging, dementia, intoxication, prefrontal injury and others. Mental continuity
as described here may be an integral element of sentience and intentionality
and may be a strong candidate for a “neural correlate of consciousness.” Is it
possible that an individual’s identity and “self” may directly correspond to
this wandering, gradually transforming distribution of temporarily sustained
representations?
The full article based on this poster can be found here:
http://www.sciencedirect.com/science/article/pii/S0031938416308289
If you found this
interesting, please visit aithought.com. The site delves into my model of
working memory and its application to AI, illustrating how human thought
patterns can be emulated to achieve machine consciousness and
superintelligence. Featuring over 50 detailed figures, the article provides a
visually engaging exploration of how bridging the gap between psychology and
neuroscience can unlock the future of intelligent machines.
