Chronically implanted semi-micro electrodes in cortical and subcortical areas of the squirrel monkey brain provided stable recordings of the potentials evoked by flash stimuli of frequencies in the range of 1-4 Hz, for periods in excess of one year. During habituation by repeated presentation of the flash stimulus, changes occurred in the amplitudes of the average evoked potentials (AEPs), most of which could be ascribed to changes in the level of arousal of the animals as assessed by the appearance of synchrony in the EEG. During conditioning and instrumental learning, when a fruit juice reinforcement became associated with the flash stimulus, further changes in the amplitudes and forms of the evoked potentials occurred which were ascribed to changes in the experimental situation and to the acquisition of the stimulus-reinforcement and the stimulus-response-reinforcement associations. Two subjects successfully completed a discrimination learning task in which discrimination of two flash rates was facilitated by a juice reinforcement for a lick response to the CS+ flash rate and an air-puff reinforcement for not withholding a response to the CS- flash rate. Changes in amplitude and forms of the AEPs were again related to situational novelty and to the acquisition of learning. No differences were observed in the AEPs derived from trials in which correct or incorrect responses were given. Presentation to one subject of flash rates intermediate to the CS+ and CS- rates resulted in behavioural generalisation. It was noted that the form of the AEP was dependent on whether the behavioural response was appropriate to the CS+ or the CS-. It was possible that this apparent 'readout from memory' was an artefact caused by sampling bias. Spectral analysis of the EEG following a juice reward failed to reveal EEG activity characteristic of the 'post reward synchrony' previously reported in rats.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:593439 |
| Date | January 1977 |
| Creators | Simpson, M. |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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