Carvell, PhD, PTUniversity
IMAGING STUDIES IN HUMAN SUBJECTS:
Imaging Studies provide an indirect measure of local brain activity or tissue perfusion.
in neuronal discharge can only be inferred by the change in metabolic demand that is indirectly measured
by the imaging techniques.
Moment by moment
alterations in synaptic potentials, membrane potentials and action potentials cannot be 'seen' by
current imaging techniques in human subjects.
'Lighting up' a
brain area does not necessarily indicate a greater level of excitatory
the cells that have the greatest metabolic demand are inhibitory neurons that influence local circuits in the
cortex or in deeper gray structures, e.g., basal ganglia and cerebellum.
McCasland and L.S. Hibbard, GABAergic Neurons in Barrel Cortex Show Strong,
Whisker-Dependent Metabolic Activation
During Normal Behavior. J Neurosci 17: 5509-5527, 1997.