Identification of neurons specifically activated after recall of context fear conditioning

The learning of new information and recall of that information presumably involves modification of and access to shared circuitry in the brain. However, learning and recall may involve the activation of distinct parts of that circuitry, according to the quite distinct functional differences between these two processes. Previously we examined neuronal activation following learning of context fear conditioning. Using the Fos-Tau-LacZ (FTL) transgenic mouse to label activated neurons, we identified a number of distinct populations of neurons in amygdala and hypothalamus which showed learning specific activation. These populations of neurons showed much less activation following recall. Here we ask what populations of neurons might be specifically activated following recall. We trained mice in context fear conditioning, and then looked at FTL activation following recall of context fear. We identified a number of populations of neurons which showed recall specific activation in nucleus accumbens shell, the anterio-medial bed nucleus of stria terminalis, the anterior commissural nucleus and the periventricular hypothalamic nucleus. These were all different populations of neurons compared with those activated following context fear learning. These different functional activation patterns occurring between learning and recall may reflect the different brain functions occurring between these two memory related processes.

► We examined brain activation following recall of fear memory.
► We found activated populations of neurons only in basal forebrain and hypothalamus.
► The basal forebrain neurons were in nucleus accumbens and BNST.
► In the hypothalamus, they were in periventricular and anterior commissural nuclei.
► These areas were distinctly different from those found in fear learning.