Molecular identification of aspartate N-acetyltransferase and its mutation in hypoacetylaspartia.

The brain-specific compound NAA (N-acetylaspartate) occurs almost exclusively in neurons, where its concentration reaches approx. 20 mM. Its abundance is determined in patients by MRS (magnetic resonance spectroscopy) to assess neuronal density and health.

The challenge of non-invasive cognitive physiology of the human brain: how to negotiate the irrelevant background noise without spoiling the recorded data through electronic averaging.

Brain mechanisms involved in selective attention in humans can be studied by measures of regional blood flow and metabolism (by positron emission tomography) which help identify the various locations with enhanced activities over a period of time of seconds. The physiological measures provided by scalp-recorded brain electrical potentials have a better resolution (milliseconds) and can reveal the actual sequences of distinct neural events and their precise timing. We studied selective attention to sensory inputs from fingers because the brain somatic representations are deployed over the brain convexity under the scalp thereby making it possible to assess distinct stages of cortical processing and representation through their characteristic scalp topographies.

Failure to recognise objects by active touch (astereognosia) results from lesion of parietal-cortex representation of finger kinaesthesis.

The inability to identify objects by manipulation with eyes closed (astereognosia) results from a focal cortical lesion of the second order parietal area 2, which integrates inputs from finger joints with tactile information.