Good news!
From President FDR's inaugural address: "... So, first of all, let me assert my firm belief that the only thing we have to fear is fear itself—nameless, unreasoning, unjustified terror which paralyzes needed efforts to convert retreat into advance. ..." (Source)
"... In a new study, researchers presented laboratory mice with an expanding overhead shadow—mimicking the approach of an aerial predator. Although the rodents initially fled in terror, they learned after repeated exposures to remain calm. By inserting probes into the animals’ brains, the scientists determined that a neural pathway connecting the visual cortex to an area of the brain called the ventrolateral geniculate nucleus (vLGN) helps mice suppress their instinctive fear responses. While the visual areas are essential to the learning process, they were surprised to find that the vLGN is crucial for storing learning-induced memories.
“Our results challenge traditional views about learning and memory,” ... noting that the outer layer of the brain—as opposed to deeper structures like the vLGN—has typically been associated with learning, memory, and behavioral flexibility. Studying these same brain circuits in humans, ... could potentially lead to treatments for conditions such as phobias, anxiety, and PTSD."
"... The research team ... mapped out how the brain learns to suppress responses to perceived threats that prove harmless over time. ..."
From the editor's summary and abstract:
"Editor’s summary
It has been proposed that one of the many functions of the sensory cortex is to modify the vigor of instinctive responses by modulation of subcortical circuits. Mederos et al. uncovered a subcortical synaptic plasticity mechanism for learning to suppress instinctive defensive behavior. The critical pathway was the projection from higher-order visual areas posterolateral of the primary visual cortex (area V1) to the ventral lateral geniculate nucleus (vLGN), which modulated instinctive fear responses based on experience. After learning, this pathway was no longer needed. This learning-induced plasticity involved endocannabinoid-mediated long-term suppression of inhibitory synapses onto vLGN neurons activated by posterolateral higher-order visual areas, which decreased presynaptic release probability. ...
Abstract
Fast instinctive responses to environmental stimuli can be crucial for survival but are not always optimal. Animals can adapt their behavior and suppress instinctive reactions, but the neural pathways mediating such ethologically relevant forms of learning remain unclear.
We found that posterolateral higher visual areas (plHVAs) are crucial for learning to suppress escapes from innate visual threats through a top-down pathway to the ventrolateral geniculate nucleus (vLGN).
plHVAs are no longer necessary after learning; instead, the learned behavior relies on plasticity within vLGN populations that exert inhibitory control over escape responses.
vLGN neurons receiving input from plHVAs enhance their responses to visual threat stimuli during learning through endocannabinoid-mediated long-term suppression of their inhibitory inputs. We thus reveal the detailed circuit, cellular, and synaptic mechanisms underlying experience-dependent suppression of fear responses."
Scientists discover brain mechanism that helps overcome fear (original news release) "The precise brain mechanisms that enable animals to overcome instinctive fears have been unveiled."
Overwriting an instinct: Visual cortex instructs learning to suppress fear responses (no public access)
Overwriting an instinct: visual cortex instructs learning to suppress fear responses (open access, preprint)
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