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Dissertation
Year: 2015 Publisher: Leuven : KU Leuven. Faculteit Psychologie en Pedagogische Wetenschappen
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Long-term potentiation (LTP) and long-term depression (LTD) are important models for the cellular and molecular mechanisms (synaptic changes) during learning and memory. High-frequency intermittent neuronal stimulation induces LTP, whereas low-frequency neuronal stimulation induces LTD. Over the last forty years, scientific research on animals -first in vitro, later in vivo- has provided valuable information on the mechanisms behind LTP and LTD. In humans, similar LTP and LTD-like effects have been induced through repetitive Transcranial Magnetic Stimulation (rTMS), Interventional Paired Associative Stimulation (IPAS) and more recently even via sensory stimulation. These relatively new non-invasive techniques show similarities with LTP/LTD, although direct evidence of synaptic plasticity alteration is still lacking. A pioneering study applying sensory LTP/LTD-like stimulation was performed by Beste et al. (2011), and revealed an effect of visual stimulation on low-level visual learning and performance. A previous study in our laboratory (Huysmans, 2014) confirmed that bilateral stimulation with high-level visual stimuli (i.e., faces) could passively modulate face discrimination performance in a frequency-dependent manner, (i.e., high-frequency stimulation improves whereas low-frequency stimulation reduces performance).In the current study we extend the feasibility of improving face-identity discrimination via LTP-like passive visual stimulation by testing hemifield/hemisphere-specific effects. Typically developing young adults (18 to 27 years old) performed a challenging face discrimination task before and after a sensory stimulation protocol. Each participant received unilateral visual stimulation, either at a high-frequency (LTP-like: 10Hz) or low-frequency (LTD-like: 1Hz) flickering rate. Two possible results were predicted: (1) learning effects could be restricted to the stimulated hemifield only or (2) effects could transfer to the other hemifield. Results confirmed our previous findings of face processing performance modulation by passive sensory stimulation, in a hemifield-specific manner, suggesting no hemispheric transfer. An unexpected 'visual saturation effect' was found immediately after the stimulation. This effect was present both in the low- and in the high-frequency stimulation condition, and resulted in temporarily impoverished performance for faces displayed in the stimulated hemifield.This and future similar studies may contribute to the development of methods to study visual learning in a bottom-up (strategic-free) way. Finally, the use of LTP-like sensory stimulation paradigms may become a therapeutic tool to improve high-level visual performance for clinical purposes (e.g., individuals with ASD or prosopagnosia).
Dissertation
Year: 2015 Publisher: Leuven : KU Leuven. Faculteit Psychologie en Pedagogische Wetenschappen
Abstract | Keywords | Export | Availability | Bookmark
Loading...Choose an application
- Reference Manager
- EndNote
- RefWorks (Direct export to RefWorks)
Long term potentiation (LTP) is a well-established model of learning. High frequency stimulation of neural tissue increases the synaptic strength of this tissue. An opposed mechanism, long-term depression (LTD), weakens the strength between synapses when trains of low-frequency stimulation are applied. Applying the protocols of LTP and LTD using mere passive sensorial stimulation has also been shown to increase or decrease perceptual learning in multiple experiments. We used a paradigm to passively stimulate either a relevant or irrelevant feature of face stimuli, and examined the effect of this feature-specific stimuli in a change-detection task. Two experiments, conducted previously in the laboratory of biological psychology, showed there is a frequency-dependent effect of passive stimulation (LTP-like or LTD-like) on a subsequent change-detection task where participants had to indicate where identity changes occurred. In our experiment, we tried to gain a further understanding of the characteristics of this passive stimulation using the same stimuli. Contrary to the previous experiments, we included a break of one hour between stimulation and the measure of performance, and we used a different stimulation protocol and added a control group. This break was used to investigate whether the effect lasted for a minimum of an hour, and we took advantage of this break by administering some questionnaires. The different stimulation protocol was added to see if stimulating an irrelevant feature deteriorates performance, as this has been shown using low-level bar stimuli. We try to extend the findings obtained with low-level stimuli to high-level face stimuli. This could provide a powerful tool to study high level visual processing and it could serve clinical purposes. We stimulated participants, using high frequent LTP-like visual stimulation, on either a relevant facial feature (identity changes), or an irrelevant feature (angle of face presentation), alongside a control group with no stimulation. We hypothesized there would be a feature-specific effect of this stimulation on the performance on a change-detection task but did not find any evidence for this hypothesis. On the contrary, a Bayesian analysis showed there is substantial evidence for the null-hypothesis. We also explored the relation between this kind of learning and some measures obtained from questionnaires (physiological and ASD measures) and found that level of satiation and level of physical activity are possibly related to the learning of the whole sample and that some ASD-measures have a differential effect on learning in the 3 groups.
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