Anxiety and depression: A top‐down, bottom‐up model of circuit function

Abstract

A functional interplay of bottom‐up and top‐down processing allows an individual to appropriately respond to the dynamic environment around them. These processing modalities can be represented as attractor states using a dynamical systems model of the brain. The transition probability to move from one attractor state to another is dependent on the stability, depth, neuromodulatory tone, and tonic changes in plasticity. However, how does the relationship between these states change in disease states, such as anxiety or depression? We describe bottom‐up and top‐down processing from Marr's computational‐algorithmic‐implementation perspective to understand depressive and anxious disease states. We illustrate examples of bottom‐up processing as basolateral amygdala signaling and projections and top‐down processing as medial prefrontal cortex internal signaling and projections. Understanding these internal processing dynamics can help us better model the multifaceted elements of anxiety and depression.

Excitatory and Inhibitory neurochemical markers of anxiety in young females

“…Assembling this evidence, we support the conceptualisation of the neurocircuitry of anxious states as an imbalanced attractor network referenced by glutamatergic activity as proposed by LeDuke and colleagues (2023), whereby over-inhibition may boost sensory processing and/or impair higher order cognition, with the caveat that thorough investigation of the neurochemistry of different nodes involved in top-down and bottom-up processing is required. For now, we conceive our findings to represent a neural over-inhibition hypothesis of anxiety.…”

“…In computational neuroscience, functional stability in operational brain circuitry is described as an attractor network (Khona & Fiete, 2022), a sub-system of cooperating units in a dynamic system. The neural circuitry of anxiety has been described in a dynamic systems network of feedback loops that hinge on the balance of glutamate and GABA neurotransmitters (LeDuke et al, 2023). It has been proposed that anxious states are reached and maintained by the tipping of a stable attractor network towards dominance of bottom-up processing (e.g., sensory driven) over top-down processing (e.g., cognitively evaluated) (LeDuke et al, 2023).…”

Neuropeptide Signaling is Required to Implement a Line Attractor Encoding a Persistent Internal Behavioral State

“…Finally, neuropeptides such as CRH 101 and NkB 30,102 are known to mediate responses to psychological stressors, which are known etiological factors in some neuropsychiatric disorders. It has been proposed that these disorders may reflect changes in attractor dynamics in certain brain regions 103 . Our data suggest that such changes could potentially result from stress-induced alterations in neuropeptide signaling 104,105 that is necessary for attractor formation.…”

Rat Anterior Insula Symmetrically Represents Tickling-Induced Playful Emotions

“…Researchers have achieved significant advancements in understanding their categorization and the brain regions involved in their expression in particular the limbic system [31][32][33][34]. Much of the focus in affective neuroscience has traditionally been on negative emotions such as fear and anxiety [35][36][37][38][39][40], providing valuable insights into the neural substrates of aversive states. Recently, the interest has expanded to encompass positive emotions.…”