Factors modulating neural processing time measured using fMRI

Resumo

Morphometric features of the hemodynamic response function (HRF) potentially provide a window on to alternative characteristics of neuronal activity using fMRI. Recently, neural processing time (NPT) - the period for which event-related neuonal activity occurs - was proposed as a measurable feature of the biophysical model of HRF. However, systematic investigation of the factors modulating NPT has not yet been conducted but could potentially mark a significant improvement of our understanding of the neural conditions characteristic of efficient information processing. Accordingly, we propose a collaborative study which will adapt NPT inference, developed at USP, to test four principal hypotheses on N-back data previously collected at KCL: (i) that NPT in decision-making regions will be modulated by working memory load, being shorter in low memory-load conditions; (ii) that individuals with psychosis will exhibit aberrant NPT on account of diminished cortical efficiency, with psychosis-related differences moderated by symptom profile; (iii) that this aberrance will be mirrored by healthy individuals following amphetamine sensitisation; and (iv) that simultaneously acquired electroencephalography (EEG)-fMRI data collected during working memory performance will provide a means of further validating NPT by permitting the assessment of the relationship between neuroelectric components (from EEG) and fMRI NPT measures. (AU)