232 — Anxiety Cells in a Hippocampal-Hypothalamic Circuit

I know that this wasn’t supposed to be a philosophical paper, but I really like this first sentence:

“Fear and anxiety are emotional responses to perceived threats, with proximal threats eliciting fear and distal threats eliciting anxiety.”

Traditionally it is generally accepted that the hippocampus contains contextual information only, without valency — in other words, this information is ‘unopinionated’ as to whether an input is a good or bad stimulus: Instead, it is expected that the outputs of the hippocampus will determine valence.

Recently, it has become clear that ventral CA1 (ventral hippocampus) encodes substantial amounts of anxiety-related information (and projects to regions associated with anxiety, fear, and mood, such as the basal amygdala), whereas dorsal hippocampus carries more spatially-based information. Place cells — fundamental for spatial reasoning and navigation — are more finely tuned in dorsal rather than ventral hippocampus as well, which substantiates this.

This paper demonstrates that vCA1 projects to the lateral hypothalamic area, and ablating these connections nulls certain types of anxiety-avoidance-related behaviors. But ablating projections from vCA1 to basal amygdala doesn’t have the same effect: Instead, these connections seem to represent fear-related responses.

This means that anxiety (far-away worries) and fear (nearby worries) are (at least partially) controlled by different circuits, and avoidance versus escape are (at least partially) different processes.