Biomedical subjects

J H Fallon

Publications and source records attributed to J H Fallon.

75 records · Page 5Linked to original sources

PubMedDate not supplied

Monoamine innervation of the forebrain: collateralization.

The forebrain is characterized by a dense, localized dopamine (DA) innervation pattern, a diffuse, widespread norepinephrine (NE) innervation pattern, and a serotonin (5-HT) innervation intermediate between the DA and NE patterns. These innervation patterns have implied that basic differences exist in the way DA, NE and 5-HT axons collateralize to different brain structures; that is, DA axons are thought to be poorly collateralized and NE and 5-HT axons are presumed to be more highly collateralized. In the present study, we used injections of retrograde labeling fluorescent dyes into various forebrain regions in order to determine axonal branching patterns from nuclei that contain DA, NE and 5-HT neurons, namely the substantia nigra-ventral tegmental area (SN-VTA), locus coeruleus (LC) and raphe nuclei (DR-MR). The results suggest that at least two subpopulations of neurons can be defined in each monoamine nucleus with respect to the way their axons collateralize. Each area contains a centrally located nuclear area with highly collateralized neurons, and more peripherally situated areas with less highly collateralized neurons. Thus, previous suppositions of the branching of monoamine axons must be revised to account for the existence of cells exhibiting totally different collateralization patterns within each monoamine nucleus.

Animals↗

PubMedDate not supplied

The development of structure and function in the postnatal human cerebral cortex from birth to 72 months: changes in thickness of layers II and III co-relate to the onset of new age-specific behaviors.

HYPOTHESIS: The thickness of a cortical layer is a composite measure of neuronal, axonal, dendritic, synaptic, and glial numbers and sizes that may relate to thefunction of a cortical area. METHODS: 35 age-specific behaviors with defined cortical localization whose onset lies between birth and 72 months were selected. Each behavior's function localized to one or more of 12 cytoarchitectonic areas (Brodmann areas 4, with homuncular subdivisions for leg, trunk, face, and hand, plus 17, 18, 19, 20, 21, 24, 36, and 37). Data on cortical thickness for each layer of 41 cytoarchitectonic areas (including the 12 above) of the postnatal human cerebral cortex from birth of 72 months were analyzed for general patterns of change. For the 12 cortical areas functionally related to theage-specific behaviors, we searched for layer thickness changes that co-related to when the behaviors began. RESULTS: Without exception, all layers of the 41 cortical areas of the postnatal human cerebral cortex studied develop through a series of repeated thinning and thickening in a wave-like fashion. With regard to the co-relation of behavioral onset and changes in cortical layer thickness, from birth to 15 months, only layer II has agreater than expected frequency of being the layer with the greatest relative change in thickness (relative to its previous value). From 15 to 72 months, only layer IlI has a greater than expected frequency of being the layer with the greatest absolute change in thickness (81% involved a change in its direction of growth (thinning <--> thickening)). The co-occurrence of directional growth change and having the greatest layer thickness change were only statistically significant for layer III when an age-specific behavior began and was not seen for the 41 cortical areas overall (p = 0.014). CONCLUSIONS: Cortical laminar development exhibits aprocess that is mathematically consistent with a random walk with drift and with boundaries so that uncontrolled proliferation and pruning are prevented. The directional changes in layer growth could be controlled by feedback coupled with growth promoting and growth inhibiting factors. Layer II, with its function of establishing local corticocortical connections, appears to be most important in establishing age-specific behaviors of infants from birth to 15 months. Such a process tends to produce relatively simpler behaviors. LayerIII, with its function of establishing longer distance corticocortical connections, appears to be most important in establishing age-specific behaviors of children from 15 to 72 months. This process tends to produce richer, more cross-modal behaviors than those mediated primarily by local corticocortical interactions.

Aging↗

PubMedDate not supplied

The cerebral neurobiology of anxiety, anxiety displacement, and anxiety denial.

BACKGROUND: Previous studies examining the relationship of anxiety scores, derived from the content analysis of speech of normal individuals, have revealed that the anxiety scores occurring in the dreams associated with rapid eye movement (REM) sleep are significantly correlated with localized cerebral glucose metabolic rates assessed by positron emission tomography (PET) scanning. These significant intercorrelations occur in different cerebral areas when the anxiety scores are obtained from mental experiences reported during non-REM sleep or during wakeful silent mentation. OBJECTIVE: The purpose of the present study was to examine the intercorrelations found between anxiety attributed to the self, anxiety-displacement, and anxiety denial measured from computerized content analysis of 5-min verbal reports of subjective thoughts and feelings obtained from wakeful normal subjects and localized cerebral glucose metabolic rates during PET scanning. METHODS: The subjects were 10 wakeful young males. Their anxiety scores were derived from computerized content analysis of 5-min reports they gave of their subjective thoughts, feelings and fantasies during a 30-min period following an intravenous injection of F D-deoxyglucose (FDG). The subjects were moved 32--45 min after this injection to obtain a PET scan, which records all of the localized cerebral glucose metabolic rates during the 30 min following the FDG injection. RESULTS: Significant intercorrelations of localized cerebral glucose metabolic rates with the scores of self-anxiety, anxiety displacement, and anxiety-denial were found in dissimilar cerebral locations depending on the type of anxiety involved. The significant correlations occurred in brain regions known to be associated with the functions of emotions, cognition, memory, and vision. CONCLUSIONS: Specific combinations of cerebral areas, based on glucose metabolic rates, appear to distinguish and be associated with different verbal expressions of anxiety. Replication of this preliminary research will be carried out.

Adult↗