Background firing rates of orbitofrontal neurons reflect specific characteristics of operant sessions and modulate phasic responses to reward-associated cues and behavior.
ABSTRACT The orbitofrontal cortex plays an important role in the ability of animals to adjust their behavior in response to behavioral outcomes. Multiple studies have demonstrated that responses of orbitofrontal neurons during operant sessions reflect the outcome of particular behaviors. These studies have focused on rapid neural responses to short-duration events such as instrumental behavior and reward-associated discrete cues. We hypothesize that longer-lasting changes in firing are also important for information processing in the orbitofrontal cortex. In the present study, we recorded the activity of 115 single orbitofrontal neurons during a multiphase operant task in which the relationship between a lever-press response and a sucrose reward was varied between the different phases. Approximately one-half of the orbitofrontal neurons exhibited a change in background firing during the operant phases. These changes were observable across multiple behavioral and stimulus events and thus reflected a general shift in background firing. The majority of changes were selective for one or the other of the operant phases. Selective changes contributed to unique patterns of phasic firing time locked to cues and operant behavior in the two operant phases. These findings are consistent with the interpretation that changes in background firing of orbitofrontal neurons reflect operant session characteristics associated with behavioral outcome, and indicate further that changes in background firing contribute to the outcome selectivity of phasic firing patterns. More generally, we propose that the background firing rates of orbitofrontal neurons reflect contextual information, and facilitate context-appropriate event-related information processing and behavioral responses.
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ABSTRACT: Based on neuro-imaging studies in cocaine-addicted humans, it is hypothesized that increases in neural activity within several regions of the prefrontal cortex contribute to cue-induced cocaine seeking and cocaine-induced compulsive drug self-administration. However, electrophysiological tests of these hypotheses are lacking. In the present study, animals were trained to self-administer cocaine (0.75 mg/kg) for 14 days. On the 14th day, we conducted electrophysiological recordings of lateral orbitofrontal (LO) and ventral anterior insula (AIV) neurons. A subset of the combined population of recorded neurons showed a change in firing rate in association with one or more of the following discrete events: (1) presentation of a discriminative stimulus that signaled the onset of the self-administration session, (2) occurrence of the first cocaine-directed operant response, (3) occurrence of a cocaine-reinforced press, and (4) presentation of cues normally paired with delivery of the cocaine reinforcer. The majority of the stimulus- and response-related changes in firing involved a brief increase in firing during the stimulus and response event, respectively. In addition to these event-specific responses, approximately half of the recorded neurons exhibited a sustained change in average firing (i.e., discharges per 30-s bin) during the cocaine self-administration session, relative to average firing during a presession, drug-free period (referred to as session changes). The prevalence of session-increases and decreases were not significantly different. These and other findings are discussed in relation to hypotheses about cue-evoked and cocaine-maintained cocaine-directed behavior.Synapse 01/2010; 64(1):1-13. DOI:10.1002/syn.20698 · 2.43 Impact Factor
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ABSTRACT: Adaptive execution and inhibition of behavior are guided by the activity of neuronal populations across multiple frontal cortical areas. The rodent medial prefrontal cortex has been well studied with respect to these behaviors, influencing behavioral execution/inhibition based on context. Other frontal regions, in particular the orbitofrontal cortex (OFC), are critical in directing behavior to obtain rewards, but the relationship between OFC neuronal activity and response execution or inhibition has been poorly characterized. In particular, little is known about OFC with respect to extinction learning, an important example of context-guided response inhibition. Here, we recorded the activity of OFC neurons while rats performed a discriminative-stimulus (DS)-driven sucrose-seeking task followed by multiple days of extinction of the DS. OFC neuronal activity was maximally responsive (1) to reward-predicting stimuli (RS) that triggered a lever press (i.e., lever-response initiation) and (2) during reward-well approach in pursuit of sucrose (i.e., well-response initiation). RS presentation that was not followed by a lever press or RS presentation during extinction produced weak activation, as did nonrewarded stimulus (NS) presentation regardless of response (press or withhold) or session (DS-sucrose or extinction). Activity related to nonrewarded well entry was minor, and activity was significantly inhibited during reward consumption. Finally, OFC neuronal activity switched selectivity to track rewarded behaviors when the RS/NS contingencies were reversed. Thus, rather than signaling variables related to extinction or response inhibition, activity in OFC was strongest at the initiation of multiple components of reward-seeking behavior, most prominently when valid reward-predicting cues drove these behaviors.The Journal of Neuroscience : The Official Journal of the Society for Neuroscience 07/2014; 34(31):10234-10246. DOI:10.1523/JNEUROSCI.3216-13.2014 · 6.75 Impact Factor
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ABSTRACT: This paper seeks to elucidate the design and implementation of an instrumentation amplifier, filters, LabVIEW-based spike detection, and automatic spike counting to detect pleasure sensation in the rat using invasive BCI. This method involved sites related to pleasure, and after acquiring signals from the ventral pallidum, facial motor cortex, and orbitofrontal cortex, these signals were analyzed to assess the pleasure sensation in the rat. The results illustrated a decreased spike rate in the motor and orbitofrontal cortices and an increased spike rate in the ventral pallidum during pleasure. The pleasure detection experiment was conducted four times to obtain the mean values of spike rates. The motor cortex had 9spikes/s, the orbitofrontal cortex had 18spikes/s and the ventral pallidum had 34spikes/s. The correlation coefficient is above 78%, effectiveness of the experiment.Measurement 01/2011; 44(1):121-128. DOI:10.1016/j.measurement.2010.09.034 · 1.53 Impact Factor