Biomedical subjects

Matthew C Hagen

Publications and source records attributed to Matthew C Hagen.

4 recordsLinked to original sources

PubMed2006

About the mechanisms of auditory verbal hallucinations: a positron emission tomographic study.

OBJECTIVE: Auditory verbal hallucinations (AVHs) likely result from disorders, as yet unspecified, of the neural mechanisms of language. Here we examine the functional neuroanatomy of single-word reading in patients with and without a history of AVH. METHOD: Eighteen medicated schizophrenia patients (8 with AVH and 10 without AVH) and 12 healthy control subjects were scanned with PET (15)O-water technique under 2 conditions: reading aloud English nouns and passively looking at English nouns without reading them. RESULTS: The contrast between the 2 conditions shows higher activation in Wernicke's area during the reading condition in the patient group and a reversed laterality index for the supplementary motor area in the AVH group. CONCLUSIONS: These findings provide indications about the possible mechanisms of AVH. We suggest that the abnormal laterality of the supplementary motor area activity accounts for the failure to attribute speech generated by one's own brain to one's self and that the activation of Wernicke's area accounts for the perceptual nature (hearing) of the patient's experience.

Adult↗

PubMed2002

PET studies of somatosensory processing of light touch.

The studies discussed in this report investigate the neural mechanisms involved in processing a light tactile stimulus as measured by positron emission tomography (PET). This light tactile stimulus (a 2-Hz tap with a von Frey hair) produced a significant increase in regional cerebral blood flow (rCBF) in contralateral primary somatosensory cortex (SI) and bilateral secondary somatosensory cortex (SII), with a larger response in the side contralateral to the stimulus. Light tactile stimulation also produced activity in multiple discrete areas in the human inferior parietal lobule (IPL), which we believe to comprise a region homologous to the monkey area 7b or feline tertiary somatosensory cortex (SIII). Directing attention to the tactile stimulus increased blood flow to SIII and activated a right-lateralized cortical network, regardless of the side of body stimulated. Directed attention to the stimulus decreased blood flow to visual cortex, but minimally modulated SI rCBF.

Adult↗

PubMed2002

Tactile motion activates the human middle temporal/V5 (MT/V5) complex.

The human middle temporal/V5 complex (hMT/V5) plays a central role in the perception of visual motion. This region is considered a unimodal visual area with little direct involvement of other sensory modalities. The current study uses H215O PET to test whether tactile motion influences the activity of hMT/V5. Regional cerebral blood flow (rCBF) within hMT/V5 was estimated in eight subjects in separate tactile motion and visual motion conditions, each contrasted with a resting, control. The tactile motion condition involved a brush stroked proximal-to-distal along the volar forearm and palm, while the subject attended to the stimulus with closed eyes. The visual motion condition consisted of low contrast, grey-scale rings radiating at 15 degrees /s from a central point, upon which the subject was instructed to fixate. The location of hMT/V5 was defined for each subject separately as the local maximum of rCBF change during the visual motion condition (vs. control). The average change in rCBF within spherical regions of interest at each peak revealed significant bilateral activation of hMT/V5 in the tactile motion condition contrasted with a second, independent set of control scans. Additionally, a single subject received a sufficient number of scans to perform a pixel-wise, within-subject analysis. His functional images were coregistered to his anatomical MRI. In this subject, tactile motion produced a significant increase in rCBF that directly overlapped a region activated by visual motion at the posterior continuance of the inferior temporal sulcus, consistent with the known location of hMT/V5. These results suggest involvement of the hMT/V5 complex in tactile motion processing.

Adult↗

PubMed2002

Somatosensory processing in the human inferior prefrontal cortex.

Three inferior prefrontal regions in the monkey receive afferents from somatosensory cortices: the orbitofrontal cortex (OFC), the ventral area of the principal sulcus, and the anterior frontal operculum. To determine whether these areas show responses to tactile stimuli in humans, we examined data from an ongoing series of PET studies of somatosensory processing. Unlike previous work showing ventral frontal activity to hedonic (pleasant/unpleasant) sensory stimulation, the tactile stimuli used in these studies had a neutral hedonic valence. Our data provide evidence for at least two discrete ventral frontal brain regions responsive to somatosensory stimulation: 1) the posterior inferior frontal gyrus (IFG) and adjacent anterior frontal operculum, and 2) the OFC. The former region (posterior IFG/anterior frontal operculum) may have a more specific role in attending to tactile stimuli.

Adult↗