Restorative Neurology and Neuroscience - Volume 12, issue 1

Authors: Nona, Shmaiel N.

Article Type: Research Article

Citation: Restorative Neurology and Neuroscience, vol. 12, no. 1, pp. 1-11, 1998

Authors: Gaillard, Frederic | Girman, Sergej V. | Gaillard, Afsaneh

Article Type: Research Article

Abstract: The aim of this study is to determine, as precisely as possible, the topography and the density of host afferents to visually responsive grafts of occipital embryonic cells implanted in block form into the occipital neocortex of adult rats. The presence of visual activity in the grafts was assessed through field potential and single unit electrophysiological recordings. Field potentials appeared triphasic in shape, had low peak-to-peak amplitude (= 100 μV), and had normal time latencies (~30 msec). Polarity reversal was never observed. Single unit recordings showed that graft neurons exhibited normal (desynchronized) spontaneous activity, had discrete receptive fields (~20° in …dia.), and responded to small stationary light flashes. A topic projection of the visual field in the grafts was also observed. Injections of cholera toxin sabunit B (CTB) into these responsive grafts induced retrograde labeling in almost all the brain regions normally projecting to the occipital cortical areas. The visual related cortical (Oc 1, Oc2) and thalamic (LP, LD, LGB) regions of the host provide the largest contingent (70-75%) of afferents to the graft. Finally, one of the major findings of this study is that 93-97% of the labeled cortical cells were found in cortical layers V and VI with a net preference for layer VI. A noticeable proportion of these layer VI labeled neurons (15-20%) was systematically observed in sublayer VIb, very close to, or even within, the white matter. We suggest thus that grafts inserted into the occipital cortex of adult rats receive functional visual inputs through various neuronal circuits. Visual inputs could be conveyed to graft eells by: (i) regenerating axons of geniculate neurons previously innervating the injured cortical site; (ii) formation of collateral branches from thalamic axons ending normally in the host cortex close to the graft boundary; and (iii) development of neuronal processes from cells located in the host cortex, mainly in layers V and VI of the occipital areas. Depending on multiple factors, yet unknown but very likely related to the host-graft integration, the cortical circuits might be either the principal afferent inflow to the graft or only a complement to the thalamic input. Show more

Keywords: neuronal transplantation, occipital neocortex, visual responses, adults, rats

Citation: Restorative Neurology and Neuroscience, vol. 12, no. 1, pp. 13-25, 1998

Authors: Kerkhoff, Georg

Article Type: Research Article

Abstract: Right hemispheric brain damage is often accompanied by visual neglect of contralesional hemispace as well as profound visuospatial and visuoconstructive disorders. Despite some recent improvements in the treatment of neglect, few therapeutic approaches exist for disorders of visuospatial cognition and none has dealt with the question of how both disorders can be treated in combination. In the present cross-over rehabilitation study, thirteen neglect patients first received visual exploration training for six weeks followed by visuospatial training for four weeks. Eleven patients had a right-hemispheric lesion, 2 a left-hemispheric lesion. Ten subjects had parietal cortical lesions, 3 lesions were outside the …parietal lobe. In the first treatment phase the patients received training, using computer controlled devices, intended to improve visual search and reading strategies. In the second phase of treatment, visual orientation discrimination was trained on a PC-monitor with verbal feedback by the therapist. Significant improvements were obtained after exploration training regarding the extent of visual search-field witbin the neglected hemifield, visual search performance in the whole visual field, reading time and reading errors but there was no change after visuospatial training for any of these measures. The reverse pattern was observed for visuospatial training: significant improvements were observed in line orientation judgements, clock perception, mental transposition of angles, horizontal writing and visuoconstructive abilities, but there was no change in any of these tests during exploration training. Feedback-based training of visual orientation discrimination revealed rapid (within 8-15 sessions) and stable improvements in this ability and a transfer to spatially related tasks. No significant correlations were obtained between training-related improvements and the time since brain damage for 9 of 10 tests, indicating that spontaneous recovery had no effect on the improvements during the two treatments. Likewise, no influence of age and gender on treatment progress was found. The phase-specific improvements in this study suggest that specific and differential treatment is necessary and effective for the treatment of visual exploration and visuospatial disorders in patients with visual neglect. Moreover, they indicate that feedback-based visual learning may prove an effective device in the neurorehabilitation of brain-damaged patients. Show more

Keywords: neglect, hemianopia, brain damage, recovery, reading, space perception, feedback training, neuropsychology, cross-over-design

Citation: Restorative Neurology and Neuroscience, vol. 12, no. 1, pp. 27-40, 1998

Authors: Hicks, Ramona R. | Boggs, Arden | Leider, Denise | Kraemer, Philip | Brown, Russell | Scheff, Stephen W. | Seroogy, Kim B.

Article Type: Research Article

Abstract: Previous studies have suggested that brain-derived neurotrophic factor (BDNF) is involved in memory and learning, and may be neuroprotective following various brain insults. Exercise has been found to increase BDNF mRNA levels in various brain regions, including specific subpopulations of hippocampal neurons. In the present study, we were interested in whether following traumatic brain injury, exercise could increase BDNF mRNA expression, attenuate neuropathology, and improve cognitive and neuromoter performance. We subjected adult …male Sprague-Dawley rats to a fluid percussion brain injury, followed by either 18 days of treadmill exercise or handling. Spatial memory was evaluated in a Morris Water Maze (MWM) and motor function was evaluated with a battery of neuromotor tests. Neuropathology was evaluated by measuring the cortical lesion volume and the extent of neuronal loss in the hipocampus. Expression of BDNF mRNA in the hippocampus was assessed with in situ hybridization and densitometry. Hybridization signal for BDNF mRNA was significantly increased bilaterally in the exercise group in hippocampal regions CA1 and CA3 (p<0.05), but not in the granule cell layer of the dentate gyrus. No significant differences were observed between the groups in neuropathology, spatial memory, or motor performance. This study suggests that after traumatic brain injury, exercise elevates BDNF mRNA in specific regions of the hippocampus. Show more

Keywords: brain-derived neurotrophic factor, cognition, traumatic brain injury,

Citation: Restorative Neurology and Neuroscience, vol. 12, no. 1, pp. 41-47, 1998

Authors: Suarez, I. | Bodega, G. | Fernandez, B.

Article Type: Research Article

Abstract: The response of astroglial cells in the hippocampus to long-term portacaval anastomosis (PCA), an experimental model of hepatic encephalopathy, was studied in adult male rats and compared with controls. Six months after PCA, the rat hippocampi were processed for glial fibrillary acidic protein (GFAP). GFAP-immunopositive astroglial profiles were observed in all hippocampal layers in PCA rats, but GFAP distribution differed in PCA rats and controls. In PCA rats, cell bodies and cell processes immunostained with GFAP …were observed mainly in the CA1-CA3 layers in relation to pyramidal neurons, whereas the number and length of the astroglial processes decreased in the rest of the hippocampal regions. In addition, decreased GFAP immunoreactivity in the perivascular processes was observed in PCA rats compared with controls. These results show that long-term PCA elicited different responses in GFAP expression in different hippocampal regions, which might suggest a regional variation in glial sensitivity. Show more

Keywords: astrocytes, GFAP, portacaval anastomosis, glutamate, hippocampus, immunohistochemisty

Citation: Restorative Neurology and Neuroscience, vol. 12, no. 1, pp. 49-54, 1998

Authors: Steinmetz, Helmut

Article Type: Book Review

Citation: Restorative Neurology and Neuroscience, vol. 12, no. 1, pp. 55-55, 1998

Authors: Firsching, Prof. Dr. med. R.

Article Type: Book Review

Citation: Restorative Neurology and Neuroscience, vol. 12, no. 1, pp. 56-56, 1998