Learning To Extinguish Fear: Evidence For The Prediction-Error Hypothesis
When an extinction procedure is introduced shortly after fear conditioning during consolidation, extinction of learned fear may shift from temporary to permanent and fear memory tends not to recover. It is unclear whether this increase in resistance to recovery of fear is the result of the unique state of memory that exists during consolidation or a result of the unique nature of the extinction process itself that may occur shortly after fear conditioning. The extinction process is commonly viewed as a learning process and, as such, extinction of learned fear is governed, at least theoretically, by a so-called prediction error, that is, expectation of shock occurs in the absence of shock and, as a result, learned fear is extinguished. With regard to extinction of learned fear shortly after training, the timing of the extinction procedure may coincide with a period of particularly high prediction error (i.e., with a period of high expectation of shock in the absence of shock) that, in contrast to the typical extinction procedure, results in greater resistance to recovery of fear. The present experiment tested the prediction-error hypothesis as it applies to extinction introduced immediately after acquisition of learned fear. Male Long Evans rats (240-280 g) underwent contextual fear conditioning, that is, each rat was placed in a dark compartment (120 s) followed by shock (0.8 mA, 0.5 s). The animals then remained confined, after shock, in the dark compartment for varied periods of time (30 s, 120 s, 240 s) and were given a retention test 48 h later. The confinement intervals allowed the animals to recall increasing levels of fear in the absence of shock - that is, to experience increasing levels of prediction error - and the retention test determined the impact of the prediction error on subsequent retention of fear. The results indicated, consistent with the prediction-error hypothesis, that as fear increased in the absence of shock during confinement, retention of fear decreased during the subsequent test. Specifically, confinement animals, relative to control animals - animals that were not confined to the apparatus immediately after training or that were confined 24 h after training - showed 1) increasing levels of fear (percent freezing behavior) with increasing levels of confinement and 2) decreasing levels of retention of fear during the subsequent test. These findings suggest that extinction of learned fear shortly after training may not be the result of a unique physiological state of memory that exists during consolidation, but rather of a unique psychological state (high expectation of shock) that occurs shortly after training when consolidation otherwise occurs.
Society For Neuroscience 2012 Annual Meeting
October 13-17, 2012
New Orleans, LA
Allen M. Schneider; Nicholas M. Vogt , '12; Zachary A. Kelm , '12; and William B. King , '13.
"Learning To Extinguish Fear: Evidence For The Prediction-Error Hypothesis".