Biomedical subjects

Matthew Hartley

Publications and source records attributed to Matthew Hartley.

3 recordsLinked to original sources

PubMed2006

Attention as a controller.

We investigate, by constructing suitable models, the manner in which attention and executive function are observed to interact, including some aspects of the influence of value/emotion on this interaction. Attention is modelled using the recent engineering control model (Corollary Discharge of Attention Movement, CODAM), which includes suitable working memory components. We extend this model to take account of various executive functions performed in working memory under attention control, such as rehearsal, substitution and transformation of buffered activity. How these are achieved is specified in suitable extension of CODAM. Further extensions are then made to include emotional values of stimuli. All of these extensions are supported by recent experimental brain imaging data on various working memory tasks, which are simulated with reasonable accuracy. We conclude our analysis by a discussion on the nature of cognition as seen in terms of the resulting extended attention model framework.

Attention↗

PubMed2006

The micro-structure of attention.

We investigate three possible methods of specifying the microstructure of attention feedback: contrast gain, additive and output gain, using simple single node and 3-layer cortical models composed of graded or spiking neurons. Contrast gain and additive attention are also tested in a spiking network which is simplified by mean field methods. The simulation task uses two stimuli, probe and reference, presented singly or together within the neuronal receptive fields whilst attention is directed towards or away from the receptive field. Model neurons are differentially activated in the different stimuli and attention and equilibrium potentials or average firing rates recorded depending on neuron type are recorded. We compare results for the different modes of attention and architectures with experimental single cell recordings which show how neuronal firing rates change in response to attention, with a bias towards neurons that respond more effectively to the attended stimulus, to investigate which attentional method best fits the experimental data. The simulation results are also mathematically analysed. We conclude that there is most experimental support for contrast gain, although some additional feedback gain would be possible. We propose a tentative method by which attention as contrast gain may occur in the primate brain using acetylcholine and nicotinic receptors.

Animals↗

PubMedDate not supplied

Subfield variations in hippocampal processing-components of a spatial navigation system.

The hippocampus is a part of the brain strongly linked to spatial exploration. Within it exist 'place cells' which fire preferentially when an animal is in certain regions of physical space. Recent research has shown that these place cells and their corresponding representations of space behave differently in the CA3 and CA1 subfields of the hippocampus. We review this research and show, by simulation, that these differences can be explained by a combination of known physiological features of the hippocampus and proposed variations in the rate of synaptic plasticity and connection strength between different information pathways. We suggest possible reasons for these differences, namely use of the CA1 cell field for current spatial exploration, and CA3 for longer term spatial memory.

Algorithms↗