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J H Pirch

Publications and source records attributed to J H Pirch.

At least 37 records · Page 2Linked to original sources
PubMed1981

Brain stimulation as a cue for event-related potentials in rat cortex: amphetamine effects.

Slow potential (SP) responses were recorded bilaterally from the frontal cortex of rats with permanently implanted silver-silver chloride electrodes. Trials were presented at variable intervals from 15 to 50 sec and the interval between the pulse cue and onset of the rewarding train was 2 sec. The cue stimulus was a single 0.5 msec monophasic square wave pulse of the same current intensity as rewarding stimulation (100 Hz, 500 msec train). Appropriate current strength was determined by prior testing for self-stimulation. The single pulse by itself failed to evoke an SP response but after repeated pairings, large negative SP responses developed which were bilaterally equal. These responses extinguished rapidly when rewarding stimulation was discontinued. d-Amphetamine (0.125, 0.25 and 0.5 mg/kg, SC) produced a dose-related depression of the SP response to the pulse cue, an effect comparable to that observed using an auditory cue with either food or MFB stimulation reinforcement. The results indicate that frontal cortex SP responses which develop in anticipation of a meaningful event do not require a peripheral sensory cue. Furthermore, amphetamine suppression of these SP responses is not produced via a disruption of the auditory system.

Animals↗
PubMed1981

Event-related slow potentials and activity of singly neurons in rat frontal cortex.

Event-related slow potentials and single unit activity were recorded from frontal cortex of unanesthetized, restrained rats trained to associate an auditory cue with rewarding medial forebrain bundle (MFB) stimulation. The majority of cortical units demonstrated an alteration of firing rate after the cue, with the predominant response being excitatory. The patterns of unit response during the interval between the cue and reinforcement varied considerable and few units showed a pattern which coincided temporally with the wave forms of the negative slow potential responses. These results indicate that negative cortical slow potential responses to meaningful stimuli are associated with an overall increase in activity of cortical neurons.

Acoustic Stimulation↗
PubMed1980

Correlation between steady potential baseline and event-related slow potential magnitude in the rat.

Event-related slow potential (SP) responses to a warning stimulus were recorded from rat frontal and visual cortex during performance of a reaction-time task. Measurements of steady potential baseline and magnitude of the negative SP response were obtained for individual trials (presented at variable intervals). The correlation between baseline and SP response magnitude was examined utilizing both amplitude and integrated area data. Also, averaged SP responses were obtained by selecting trials for averaging according to baseline potential. Slow potential response magnitude was inversely correlated with baseline negativity. Neither baseline nor SP response amplitude was correlated with trial number of intertrial interval. Averaged SP responses consisting of trials with more positive baselines were larger in magnitude than averaged SP responses consisting of trials with more negative baselines. The steady potential level attained during trials with more positive baselines was not more negative than the level reached during trials with negative baselines. These data are consistent with the concept of "ceiling" effect for event-related slow potentials.

Animals↗
PubMed1977

Amphetamine effects on brain slow potentials associated with discrimination in the rat.

Slow potentials were recorded from the anterior cortex of rats during discrimination conditioning and the effects of various doses of d-amphetamine on these responses were examined. In the discrimination paradigm one tone (Sd) was followed at three see after the onset by food reinforcement while another tone (S delta) indicated that no reinforcement would follow. Slow potential (SP) responses were measured during the three-sec period following onset of the stimulus. For the first several training sessions the SP responses demonstrated a phase of generalization during which responses were the same to both stimuli. Thereafter, the responses to Sd were significantly greater than responses to S delta. d-Amphetamine produced a dose-related depression of SP responses to the reinforced stimulus in doses of 0.25 to 2.0 mg/kg. The effect of amphetamine on SP responses to S delta was biphasic; the lower doses (0.25 and 0.5 mg/kg) enhanced responses, no change was seen after 1.0 mg/kg and the high dose (2.0 mg/kg) depressed responses. This study demonstrates that the rat develops differential slow potential responses to reinforced and nonreinforced stimuli in a discrimination paradigm and that d-amphetamine produces a differential and dose-related alteration of these SP responses. It is suggested that the actions of amphetamine may be produced through interference with mechanisms of discrimination, by an effect on subcortical activating systems involving norepinephrine, and/or by activation of inhibitory dopamine receptors on cortical neurons.

Animals↗