Search results for "Stimulus"
showing 10 items of 555 documents
A study of caudate inhibition on an epileptic focus in the cat hippocampus
1988
The mechanisms whereby the caudate nucleus modifies hippocampal spiking activity have been studied. Epileptiform activity was induced in the cat hippocampus by topical application of sodium penicillin in different concentrations. The frequency of induced spikes appeared to be directly correlated to the two doses of epileptogenic agent. The inhibitory effect of 10 Hz caudate stimulation on spike frequency was present even when stimulation lasted for 180 s. Likewise 25 Hz caudate stimulation brought about an inhibition which was maintained by stimulus trains lasting up to 90 s, while the degree of inhibition was reduced by trains of longer duration (120, 150 and 180 s); similar results were a…
Is pain sensitivity altered in people with Alzheimer's disease? A systematic review and meta-analysis of experimental pain research
2016
Background Clinical studies suggest people with Alzheimer's disease (AD) have altered pain sensitivity. Experimental pain research is equivocal. Objective Conduct a meta-analysis to investigate if people with AD have altered pain sensitivity compared to healthy controls (HCs). Methods Three authors searched electronic databases from inception till November 2015 for experimental pain studies in AD vs. HCs. Outcome measures were pain threshold, tolerance, pain ratings, heart rate response to noxious stimuli and the Facial Action Coding System (FACS). Random effect meta-analysis calculating Hedges' g ± 95% confidence intervals (CI) was conducted. Results Thirteen studies were identified, inclu…
The effect of explicit knowledge on sequence learning: A graded account
2004
In this paper, we study the effect of conscious knowledge on implicit sequence learning. To do so, in three sequence learning experiments, we manipulated (1) the extent to which instructions were intentional vs. incidental - intentional participants were informed of the existence of sequential regularities, and (2) the amount of explicit knowledge given to participants about the stimulus material. Results indicated that explicit knowledge improves sequence learning, as indexed by an increase in reaction times when the training sequence is unexpectedly replaced by another one. To enable us to differentiate between implicit and explicit learning, we applied the process dissociation procedure …
Event-Related Potentials (ERP) Indices of Motivation during the Effort Expenditure for Reward Task
2020
Dynamic and temporal facets of the various constructs that comprise motivation remain to be explored. Here, we adapted the Effort Expenditure for Reward Task, a well-known laboratory task used to evaluate motivation, to study the event-related potentials associated with reward processing. The Stimulus Preceding Negativity (SPN) and the P300 were utilized as motivation indicators with high density electroencephalography. The SPN was found to be more negative for difficult choices compared to easy choices, suggesting a greater level of motivation, at a neurophysiological level. The insula, a structure previously associated with both effort discounting and prediction error, was concomitantly a…
Electrophysiological evidence for change detection in speech sound patterns by anesthetized rats
2014
Human infants are able to detect changes in grammatical rules in a speech sound stream. Here, we tested whether rats have a comparable ability by using an electrophysiological measure that has been shown to reflect higher order auditory cognition even before it becomes manifested in behavioral level. Urethane-anesthetized rats were presented with a stream of sequences consisting of three pseudowords carried out at a fast pace. Frequently presented “standard” sequences had 16 variants which all had the same structure. They were occasionally replaced by acoustically novel “deviant” sequences of two different types: structurally consistent and inconsistent sequences. Two stimulus conditions we…
Early Brain Sensitivity to Word Frequency and Lexicality During Reading Aloud and Implicit Reading
2019
The present study investigated the influence of lexical word properties on the early stages of visual word processing (<250 ms) and how the dynamics of lexical access interact with task-driven top-down processes. We compared the brain's electrical response (event-related potentials, ERPs) of 39 proficient adult readers for the effects of word frequency and word lexicality during an explicit reading task versus a visual immediate-repetition detection task where no linguistic intention is required. In general, we observed that left-lateralized processes linked to perceptual expertise for reading are task independent. Moreover, there was no hint of a word frequency effect in early ERPs, while …
2015
The manner in which populations of inhibitory (INH) and excitatory (EXC) neocortical neurons collectively encode stimulus-related information is a fundamental, yet still unresolved question. Here we address this question by simultaneously recording with large-scale multi-electrode arrays (of up to 128 channels) the activity of cell ensembles (of up to 74 neurons) distributed along all layers of 3–4 neighboring cortical columns in the anesthetized adult rat somatosensory barrel cortex in vivo. Using two different whisker stimulus modalities (location and frequency) we show that individual INH neurons – classified as such according to their distinct extracellular spike waveforms – discriminat…
Integration of Peripheral Adiposity Signals and Psychological Controls of Appetite
2007
Publisher Summary This chapter presents an overview of the major anatomical and neurochemical participants in brain reward circuitry. It also elaborates the evidence available to date that supports the hypothesis that energy regulatory signals can modulate food reward. Psychological modulation of feeding involves taste hedonics and preferences, and the rewarding aspects of food. The brain circuitries implicated in stimulus reward, and in the regulation of energy balance, have traditionally been considered as separate. However, more recently, accumulated evidence suggests that there is both anatomical and functional crosstalk between these sets of central nervous system (CNS) circuitry. Addi…
Effects of pulsed high-frequency electromagnetic fields on the neuroendocrine system.
1998
The influence of pulsed high-frequency electromagnetic fields emitted from a circularly polarized antenna on the neuroendocrine system in healthy humans was investigated (900 MHz electromagnetic field, pulsed with 217 Hz, average power density 0.02 mW/cm<sup>2</sup>). Nocturnal hormone profiles of growth hormone (GH), cortisol, luteinizing hormone (LH) and melatonin were determined under polysomnographic control. An alteration in the hypothalamo-pituitary-adrenal axis activity was found with a slight, transient elevation in the cortisol serum level immediately after onset of field exposure which persisted for 1 h. For GH, LH and melatonin, no significant effects were found under…
Some Necessary Revisions of the Neuronal Model Concept of the Orienting Response
1978
Sokolov's neural trace model as well as his entropy model of the orienting response are examined. Both seem inadequate for empirical and theoretical reasons. The role of the relevance aspect of a stimulus is stressed. It is proposed to consider the information transmitted by a stimulus as in some way being weighted by the relevance of the context to which it belongs. It is furthermore proposed to restrict the neural trace concept to the physical properties of the stimulus. Major theoretical gain is achieved by viewing information content of a stimulus and its physical properties independently and by breaking the motivation determining the strength of an orienting response into a situation-s…