Investigating the functional correlates of long-term potentiation (LTP) in the human visual evoked potential (VEP)
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1
School of Psychology, University of Auckland, New Zealand
Background. Long-term potentiation (LTP) is a form of cortical plasticity that can be observed during normal brain functioning. LTP refers to the increase in synaptic strength in networks of connected cortical neurons, and has been proposed to underlie the molecular foundation of learning and memory. LTP has been studied extensively with laboratory animals, but has also has been shown non-invasively in humans using rapid visual simulation, which leads to an increase in the N1b component of visual evoked potentials (VEP). While the ability to induce LTP in humans in the laboratory has now been well-established, considerably less attention has focused on the functional behavioural consequences of increased VEP amplitude. Therefore, our aim in this research is to combine EEG with visual psychophysics to explore the relationship between LTP and behavioural performance in a perceptual learning task.
Methods. EEG was measured from 129-scalp electrodes. Prior to induction of LTP, full contrast Gabor gratings were presented at a low rate of stimulus presentation (1.5 Hz) to obtain a baseline VEP amplitude. Following that, full-contrast Gabor gratings were flashed at a higher presentation rate (10Hz) for approximately two minutes. This constituted the photic ‘tetanus’ – used to induce LTP, which is inferred through an increase in the amplitude of the N1 component. VEP amplitude was measured again post-tetanus. Contrast thresholds were also measured pre- and post-tetanus using the method of constant stimuli.
Results. Data collection and analysis are still ongoing. Preliminary analyses suggest that we will replicate past studies from our research group showing an increase in the N1 amplitude following tetanus, and that the minimum contrast required for accurate discrimination of the orientation of a Gabor grating is reduced post-tetanus.
Discussion. Results from this experiment will provide insights as to whether there are meaningful improvements in perception that accompanies LTP. If our hypotheses and initial observations are confirmed, our data will provide novel evidence of perceptual learning in the absence of task-relevant training, and would constitute the first reliable evidence that long-term potentiation of the visual evoked potential has meaningful perceptual consequences.
Keywords:
long-term potentiation (LTP),
method of constant stimuli,
visual evoked potential (VEP),
Perceptual Masking,
Perceptual Learning
Conference:
ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013.
Presentation Type:
Oral
Topic:
Sensation and Perception
Citation:
Ong
J,
Kirk
IJ and
Corballis
PM
(2013). Investigating the functional correlates of long-term potentiation (LTP) in the human visual evoked potential (VEP).
Conference Abstract:
ACNS-2013 Australasian Cognitive Neuroscience Society Conference.
doi: 10.3389/conf.fnhum.2013.212.00120
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Received:
23 Oct 2013;
Published Online:
25 Nov 2013.
*
Correspondence:
Miss. Joanne Ong, School of Psychology, University of Auckland, Auckland, New Zealand, jong016@aucklanduni.ac.nz