One aspect of my research is aimed at determining the specificity and role that selective attention plays in the somatosensory system.
One possibility is that attention is broadly tuned and nonspecific. If this is the case, then attention may function as a kind of neural "spotlight" that simply directs the animals efforts within the somatosensory system from one location on the body to another.
The most likely role that attention plays under these circumstances is to modify the gain of neurons and to enhance the responses of neurons that fall within the "spotlight" and to suppress the responses of other neurons.
Another more likely possibility is that attention is highly specific and functions to tailor the neural responses in a way that allows the animal to achieve a specific perceptual goal. For example, if the animal is performing an orientation discrimination task, then only those neurons that are orientation selective will show attention modulated responses and other neurons that lie near those neurons but are not critical for performing the task will not be affected.
To test these alternative hypothesis and to understand the role that attention plays in tactile processing in primary (SI) and secondary (SII) cortex, we are presently performing experiments on monkeys trained to perform a variety of attention tasks. These experiments are designed to selectively control the animal's focus of attention at different levels. The goal is to see how finely attention can be focused within the somatosensory system and to investigate whether attention modifies how stimuli are represented in the nervous system
We are also investigating the mechanisms of attention. These studies, which are done in collaboration with Ernst Niebur and Ken Johnson, are aimed at understanding the role of temporal synchrony in attentional selection. The hypothesis is that neurons that are processing selected information fire more synchronously than other neurons that are not within the attentional focus.
The figure shows the response of a neuron in SII cortex from an animal trained to recognize embossed letters of the alphabet that were scanned across their distal finger pads. The figure shows the response evoked by the letter "X" when the animal correctly identified the letter -"hits", "incorrectly identified the letter- "misses", or performed a visual task that was unrelated to the tactile letter- "visual task".
| Hsiao SS, Vega-Bermudez
F (2001) Attention in the Somatosensory system. In: The Somatosensory
System: Deciphering the Brain's Own Body Image (Nelson RJ, ed), pp 197-217.
Boca Raton: CRC Press. PDF |
