The pattern of cerebral activity underlying verbal fluency shown by split-dose single photon emission tomography (SPET or SPECT) in normal volunteers

Abstract

SYNOPSISUptake of 99mTc-Exametazime, a marker of relative regional cerebral blood flow has been determined with Single Photon Emission Tomography (SPET or SPECT) in 20 healthy, elderly female subjects during neuropsychological challenge. Each subject was studied under basal conditions after injection of 125 MBq 99mTc-Exametazime. Without moving the head of the subject, they were scanned again after injection of 375 MBq 99mTc-Exametazime. The second injection was made in 10 subjects during a test of verbal fluency, usually regarded as a test of the integrity of function of the left frontal cortex. In the other 10 subjects the second injection was made during simple verbalization (counting). This method of splitting the normal full dose of 99mTc-Exametazime allows a novel comparison between basal and active conditions for different brain regions. Verbal fluency was associated with reduced uptake bilaterally in the region of the basal ganglia and in left temporal (peri-sylvian) cortex when compared with calcarine cortex, an unstimulated reference sensory area. By contrast, counting produced relative activation, greatest in frontal and parietal areas. Thus, a clinically relevant neuropsychological test can be characterized metabolically by a pattern of regional brain activity, whose localization cannot readily be predicted from classical studies of brain lesions. Reduction of regional uptake may suggest an important role for de-activation or inhibition of function in human cognition. The involvement of basal ganglia and temporal areas is of particular interest in relation to the investigation of functional psychiatric illness.

The Addenbrooke's Cognitive Examination for the differential diagnosis and longitudinal assessment of patients with parkinsonian disorders

“…Interestingly, patients with PSP or CBD may generate a small number of low-frequency words (eg, ‘peramubulator’) rather than high-frequency words (eg, ‘put’, ‘people’). This is supported by evidence from functional imaging suggesting that verbal fluency is associated with activation of a diffuse cortical network26 but with an emphasis on Brodmann area 45 for lexical retrieval and Brodmann area 46 in phonological processing during word generation 27. Patients with brain lesions in the left dorsolateral frontal lobe were found to have impaired verbal fluency if there were additional or solitary striatal lesions 28.…”

Executive function and uptake of 99m Tcexametazime shown by single photon emission tomography after oral idazoxan in probable Alzheimer-type dementia

“…They also provided important evidence that frontal networks are active in performing ßuency in Alzheimer-type dementia just as they are in normals (Frith et al 1991). Interestingly, bilateral de-activation of temporal cortex seen in PET (Frith et al 1991) and SPET (Shedlack et al 1991) studies of normal subjects was not observed. A similar failure has also been observed in schizophrenic subjects and may, accordingly, be less speciÞc to that condition than was suggested .…”

Neural-network-based classification of cognitively normal, demented, Alzheimer disease and vascular dementia from single photon emission with computed tomography image data from brain.

“…Brain imaging is an important part of the diagnostic evaluation (1)(2)(3)(4). However, the brain image may be qualitatively difficult to distinguish between normal and demented persons, and more so between different dementia types such as AD and VD.…”