Detecting a touch
What happens in the brain when a stimulus is detected? How does the brain activity look when there is no such detection? This question has been addressed by study by de Lafuente et al. in a study of monkeys. Using somatosensory stimuli, the results indicated that the primary sensory cortices are not part of the neural correlates of conscious detection. On the other hand, conscious detection led to increased activity in the frontal lobes. This study corresponds nicely with theories suggesting that consciousness involves a spread network of brain areas instead of sensory-specific areas. Furthermore, this study is interesting due to its use of somatosensory stimuli, while the majority of studies on NCC is about visual perception.
Neuronal correlates of subjective sensory experience
Victor de Lafuente & Ranulfo Romo in Nature Neuroscience 8, 1698 – 1703 (2005)
When a near-threshold stimulus is presented, a sensory percept may or may not be produced. The unpredictable outcome of such perceptual judgment is believed to be determined by the activity of neurons in early sensory cortex. We analyzed the responses of neurons in primary somatosensory cortex, recorded while monkeys judged the presence or absence of threshold stimuli. We found that these responses did not covary with the monkeys’ perceptual reports. In contrast, the activity of frontal lobe neurons did covary with trial-by-trial judgments. Further control and microstimulation experiments indicated that frontal lobe neurons are closely related to the monkeys’ subjective experiences during sensory detection.
http://www.hhmi.org/research/scholars/romo.htmlRanulfo Romo homepage
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