Fast Spiking and Regular Spiking Neural Correlates of Fear Conditioning in the Medial Prefrontal Cortex of the Rat

Abstract

In order to investigate whether and how medial prefrontal cortex (mPFC) of the rat is involved in processing of information related to fear conditioning, we recorded from single units in the prelimbic and infralimbic cortex of fear-conditioned rats in response to an explicit conditional stimulus (CS; an auditory tone) or contextual cues (conditioning box). The majority of units changed their activities significantly in response to the CS in a delay or trace conditioning paradigm. Both transient and tonic activity changes, including delay cell activity, were observed as in other behavioral tasks. When exposed to the context without CS delivery, most units changed their activities as well. These results show that both tone and contextual information are processed in the rat mPFC in expectation of the delivery of an aversive stimulus (electric foot shock). Interestingly, fast spiking cells (putative inhibitory interneurons) and regular spiking cells (putative projection neurons) showed different patterns of responses. Fast spiking cells tended to show transient responses and increased their firing rates following CS presentation, whereas a complementary pattern was observed in the regular spiking cells. Our results enhance our understanding of the neural mechanisms underlying prediction of an aversive stimulus in the mPFC.

NMDA receptor hypofunction produces concomitant firing rate potentiation and burst activity reduction in the prefrontal cortex

“…A total of 518 neurons were isolated from eight rats in 27 recording sessions. Neurons were separated into 510 RS neurons (putative pyramidal neurons) and eight FS neurons (putative interneurons), based on established criteria (21)(22)(23) Three types of postinjection responses were identified in RS neurons: increased firing rate (type 1), decreased firing rate (type 2), or no change in firing rate (type 3). After saline injection, an approximately equal proportion of neurons responded with either an increase or decrease in firing rate, and 21% of the neurons had no significant change in firing rate (Fig.…”

Resolving the neural circuits of anxiety

“…By contrast, extinction of the learned fear association increases activity in BA neurons targeting the IL 105 . Fittingly, increased activity in the IL is associated with fear extinction 108 (but see also [109][110][111], and electrical stimulation of IL reduces freezing to the CS, even in animals that are resistant to extinction training 108,112 . In naïve mice, both of these subdivisions of mPFC exert similar levels of excitation and feed-forward inhibition upon BLA principal neurons.…”

Neural Correlates of Interval Timing in Rodent Prefrontal Cortex

“…The animal's head position was monitored by tracking a set of light-emitting diodes mounted on the headstage at 60 Hz. When recordings were completed, small marking lesions were made by passing an electrolytic current (50 mA, 30 s, cathodal) through one channel of each tetrode and recording locations were verified histologically as previously described (Baeg et al, 2001).…”