Computational Psychiatry and Psychometrics Based on Non-Conscious Stimuli Input and Pupil Response Output

It is well known from the technical literature that non-conscious perception of emotional stimuli
affects behavior, perception, and even decision making [e.g., see Ref. (1) for a comprehensive
review]. Non-conscious perception can be obtained by inducing sensory unawareness, e.g., through
backward masking and binocular rivalry (1). Experiments adopting such paradigms have evidenced
that non-consciously perceived emotional stimuli elicit activity in the amygdala, superior colliculus,
basal ganglia, and pulvinar. More specifically, it has been shown that a subcortical fast route exists
between the thalamus and the amygdala, which, in turn, project onto different cortical and subcortical
structures [e.g., onto the nucleus accumbens, NAcc, when appetitive stimuli are perceived (2)].
These findings agree with the hypothesis about amygdala functionality proposed by LeDoux (3, 4).
In fact, LeDoux has hypothized the existence of a thalamic pathway to the amygdala; such a pathway
would allow to automatically detect evolutionary prepared visual stimuli (such as emotional faces,
sexual-related stimuli, spiders, snakes, and injuries). Note that this model is also supported by other
results acquired by different researchers that have employed masking in normal participants (5, 6)
or have observed brain activity in patients affected by cortical blindness (7, 8). According to this
model about amygdala functionality, the superior colliculus stimulates the pulvinar nucleus of the
thalamus, which then arouses the amygdala (4, 9, 10). This suggests that salient features representing
biologically prepared stimuli could be stored in the amygdala since birth. From an evolutionary perspective,
this can be related to the fact that fast and implicit (or unconscious) reactions are needed in
dangerous and highly dynamical environments. Moreover, even ontogenetic stimuli (e.g., weapons)
are encoded within the amygdala through implicit learning during life (11, 12). These data evidence
the importance of subcortical regions associated with implicit emotional processing. In fact, since
the brain structure works like a hierarchical network (13) in which the limbic system represents a
lower hierarchical level with respect to the higher cortical structure, it is likely that the overall perception
and emotional appraisal are influenced by low-level evaluations. More specifically, the signals
coming from lower and higher hierarchical levels determine prediction errors (or error signals) at
intermediate levels; such error signals propagate through the entire hierarchical structure, determining
cognitive perception, causes attributions, emotional evaluations, actions, and behaviors (14).
Hence, if subcortical limbic-brainstem regions are defective, all the network hierarchy functioning
will be compromised. As a matter of fact, a dysfunction in the limbic-brainstem regions is associated
with various psychiatric disorders with higher cognitive deficits including autism, schizophrenia,
posttraumatic stress disorders (PTSD), attention deficits/hyperactivity disorder (ADHD), neurosis,
phobia, and others.