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PubMedDate not supplied

Suppression of visual perception by magnetic coil stimulation of human occipital cortex.

Magnetic coil (MC) stimulation percutaneously of human occipital cortex was tested on perception of 3 briefly presented, randomly generated alphabetical characters. When the visual stimulus-MC pulse interval was less than 40-60 msec, or more than 120-140 msec, letters were correctly reported; at test intervals of 80-100 msec, a blur or nothing was seen. Shifting the MC location in the transverse and rostro-caudal axes had effects consistent with the topographical representation in visual cortex, but incompatible with an effect on attention or suppression from an eyeblink. The MC pulse probably acts by eliciting IPSPs in visual cortex. The neural activity subserving letter recognition is probably transmitted from visual cortex within 140 msec of the visual stimulus.

Humans↗
PubMed1989

Neuronal correlates of subjective visual perception.

Neuronal activity in the superior temporal sulcus of monkeys, a cortical region that plays an important role in analyzing visual motion, was related to the subjective perception of movement during a visual task. Single neurons were recorded while monkeys (Macaca mulatta) discriminated the direction of motion of stimuli that could be seen moving in either of two directions during binocular rivalry. The activity of many neurons was dictated by the retinal stimulus. Other neurons, however, reflected the monkeys' reported perception of motion direction, indicating that these neurons in the superior temporal sulcus may mediate the perceptual experience of a moving object.

Action Potentials↗
PubMed1991

[Prosopagnosia. A rare disorder of visual perception].

Prosopagnosia is a rare neurological sign, characterized by disturbance of recognition of faces. It is important to remember that prosopagnosia can appear as a result of a brain injury, and as such may be a major disability to the patient. We report a case of a nine year old boy with prosopagnosia due to brain injury at the age of 18 months. The main injury was localized to the boy's left hemisphere, but his right hemisphere was probably also affected. Most post mortem examinations of patients suffering from prosopagnosia show bilateral or right-sided parietal, temporal and occipetal pathological changes.

Agnosia↗
PubMed1992

Optical imaging of architecture and function in the living brain sheds new light on cortical mechanisms underlying visual perception.

Long standing questions related to brain mechanisms underlying perception can finally be resolved by direct visualization of the architecture and function of mammalian cortex. This advance has been accomplished with the aid of two optical imaging techniques with which one can literally see how the brain functions. The upbringing of this technology required a multi-disciplinary approach integrating brain research with organic chemistry, spectroscopy, biophysics, computer sciences, optics and image processing. Beyond the technological ramifications, recent research shed new light on cortical mechanisms underlying sensory perception. Clinical applications of this technology for precise mapping of the cortical surface of patients during neurosurgery have begun. Below is a brief summary of our own research and a description of the technical specifications of the two optical imaging techniques. Like every technique, optical imaging also suffers from severe limitations. Here we mostly emphasize some of its advantages relative to all alternative imaging techniques currently in use. The limitations are critically discussed in our recent reviews. For a series of other reviews, see Cohen (1989).

Brain↗