Biomedical subjects

Tako M Horsley

Publications and source records attributed to Tako M Horsley.

4 recordsLinked to original sources

PubMed2005

Effects of stop signal modality, stop signal intensity and tracking method on inhibitory performance as determined by use of the stop signal paradigm.

In Experiment 1, the effects of stop signal modality on the speed and efficiency of the inhibition process were examined. Stop signal reaction time (SSRT) and inhibition function slope in an auditory stop signal condition were compared to SSRT and inhibition function slope in a visual stop signal condition. It was found that auditory stop signals compared to visual stop signals enhanced both the speed and efficiency of stopping. The modality effects were attributed to differences in the neurophysiological processes underlying perception. However, Experiment 2 demonstrated that the modality difference was larger for 80 dB(A) auditory stop signals than 60 dB(A) auditory stop signals. This effect was reconciled with the suggestion that loud tones are more capable of eliciting immediate arousing effects on motor processes than weak tones and visual stimuli. The second purpose of the present investigation was to explore the utility (and potential advantages) of an alternative way of setting stop signal delay relative to mean reaction time (MRT). The method that was suggested compensates for inter-individual differences in primary task reaction speed by setting stop signal delays as proportions of the subjects' MRT.

Adolescent↗

PubMed2004

Inhibitory control during sentence reading in dyslexic children.

The present study focused on the nature of the reading disability of children with the guessing subtype of dyslexia (who read fast and inaccurately). The objective was to separate the excitatory account of their reading disturbance (i.e., in guessers the words' resting levels of activation are oversensitive to semantic context) from the inhibitory account (i.e., guessers tend to react prematurely to (false) candidate words that are activated in the lexicon). To disentangle the above accounts, guessers and normal readers were presented with a sentential priming task (SPT). In the SPT, subjects had to determine whether the final word of a sentence was semantically congruent or incongruent with the sentence, but had to inhibit their 'congruent' or 'incongruent' response in case of an occasionally presented pseudoword. To evoke guessing, each pseudoword closely resembled either a valid congruent or incongruent word. Guessing referred to prematurely accepting a pseudoword as a word that either appropriately or inappropriately completed the sentence. The extent to which subjects guessed at word meaning was evidenced by the false recognition rates (FRR) of the misspelled terminal words. Analyses on the FRRs of the pseudowords showed that guessers had significantly more difficulty in suppressing the 'go tendency' triggered by the pseudowords. It was concluded that the impulsive reading style of guessers should be ascribed to a less efficient suppression mechanism rather than to excessive reliance on contextual information. Specifically, the data were explained by assuming that the availability of the pseudoword's candidate meaning activated the hand to respond with, and that guessers found difficulty in suspending this response until they analyzed all letters in the stimulus and they could be sure of its spelling.

Analysis of Variance↗

PubMed2003

Hemispheric differences in stop task performance.

This study examined hemispheric specialization for stop task performance. It was found that inhibitory performance was better for stop signals presented in the right visual field. This result provided support for the hypothesis that, during stop task performance, subjects call upon the left-lateralized neural system that is involved in active attention. It was suggested that a stop task requires such a mode of attention because subjects maintain a tonic readiness for inhibitory action while being engaged in the stop task's go routine. Subjects are continuously alert for possible stop signals while discriminating between go stimuli. The stop task may be considered a typical activation task.

Adolescent↗

PubMed2002

Fronto-central dysfunctions in reading disability depend on subtype: guessers but not spellers.

The goal of this study was to test the hypothesis that the inhibitory deficits previously found in children with the guessing subtype of dyslexia (who read fast and inaccurately) can be attributed to dysfunctions in the fronto-central brain areas. For this purpose, the electrocortical correlates of the inhibition mechanism were assessed in a stop task that was adapted for event-related brain potential recording. It was found that in children with the spelling subtype of dyslexia (who read slowly and accurately) and normal readers, a positive component with a fronto-central scalp distribution was related to processes engaged in the inhibition of a response. Guessers did not show this "inhibition P300." Analyses of the lateralized readiness potential (LRP) data suggested that response inhibition in spellers depended (at least in part) on their ability to inhibit the central activation of the response. In guessers, the association between response inhibition and inhibition of activity in the central motor structures was found to be weaker. It was concluded that the inhibitory deficits in guessers can be attributed to dysfunctions in the fronto-central brain structures involved in selective motor inhibition (indicated by the LRP data) and nonselective motor inhibition (indicated by the P300 data). It was suggested that there may be an association between guessers and attention deficit hyperactivity disorder children in that both clinical groups may suffer from the same type of deficits in executive functioning.

Analysis of Variance↗