Fear is the emotional response to a specific stimulus (real or perceived) that poses an imminent threat, whereas anxiety is the anticipation of possible threats that are obscure and undefined. In terms of responses, fear leads to autonomic arousal (e.g., increased heart rate and blood pressure) necessary for fight or flight and escape behaviors, while anxiety is associated with muscle tension and increased vigilance, cautious or avoidant behaviors.
As the two states are caused by different situations and lead to different responses, some research in recent years has focused on whether different brain circuitry may mediate fear versus anxiety. Earlier research focusing on gross brain structures had in many cases found that fear and anxiety are mediated by the same brain structures. However, technical advances in recent years have allowed scientists to look closer into those gross brain structures, and led to the finding that many of those structures host several cell populations forming neuronal circuits that are called microcircuits with different characteristics, many subregions that communicate with each other and more distant brain regions, and perform different tasks.
“Surprisingly, we found that the control of anxiety and fear is completely non-overlapping within the hippocampus…The findings suggest, said Engin, that two different microcircuits within the hippocampus need to be targeted to reduce anxiety versus fear.
“It is possible that these two microcircuits are differentially affected in different anxiety disorders, depending on whether the disorder is characterized more dominantly by disruptions in fear reactions (e.g., phobias) or in anxiety (e.g., generalized anxiety disorder),”