The Emotional Gatekeeper: A Computational Model of Attentional Selection and Suppression through the Pathway from the Amygdala to the Inhibitory Thalamic Reticular Nucleus
Fig 5
Focused top-down attention on food-related stimuli.
Axis and subplot labels are as in Fig 3. A, Plan map. B, Salience map for appetitive (positive) stimuli. C, Salience map for aversive (negative) stimuli. D, E, F, Sensory map, including sensory cortex (D), sensory TRN sector (E) and sensory thalamus (F). G, Input to sensory thalamus (stimuli and distractors). H, Reinforcement signals and Conditioned Stimuli (CSs). The simulations reveal that the amygdala-TRN projection can mediate both bottom-up (green arrows) and top-down (purple arrows) modulation of attention by emotion. During the first conditioning phase, CS1 and CS2 are associated with a food reward. During the second conditioning phase, CS3 is associated with an aversive stimulus. During the first testing phase (similar to Fig 3), the conditioned stimuli are presented repeatedly in the sequence CS1-CS3-CS2-CS3, with no reinforcement (bottom-up mode, green arrows). During testing phase 1, the rate at which the plan (A) shifts from feed (blue) to fear (red) is dependent on the rate of build-up of the plan cortical expectation violation (EV) signal. Here the cortical expectation violation signal builds up slowly (similar to Fig 3), allowing each plan (A) to persist for some time despite stimulus-specific violations of expectation. However, during the second testing phase (to the right of the vertical dotted line) top-down bias is applied to the feed plan (A–blue plot). This allows the feed plan to overcome the effects of expectation violation (EV), and remain active (in this simulation M1 = 160 during the second testing phase). Top-down excitation of BA neurons (purple arrow) allows BA (B) to direct attention only to the stimuli that were previously associated with food: CS1 and CS2. Attention to CS3 (D, F) is attenuated, despite the fact that it has been labeled as salient by virtue of its association with an aversive stimulus. Top-down cortical biasing (A) of BA can restrict attention to a particular category of affectively salient stimuli without restricting attention to only one stimulus. In other words, the system can divide attention between CS1 and CS2. Thus, even when the plan itself is locked in place by the top-down bias, there is within-plan flexibility to shift sensory attention. This flexibility arises because expectation violation signals cause inhibition of BA neurons.