Mapping of the anatomical circuit of CaM kinase-dependent courtship conditioning in Drosophila.
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Globally inhibiting CaM kinase activity in Drosophila, using a variety of genetic techniques, disrupts associative memory yet leaves visual and chemosensory perception intact. These studies implicate CaM kinase in the plastic processes underlying learning and memory but do not identify the neural circuitry that specifies the behavior. In this study, we use the GAL4/UAS binary expression system to define areas of the brain that require CaM kinase for modulation of courtship conditioning. The CaM kinase-dependent neurons that determine the response to the mated female during conditioning and those involved in formation and expression of memory were found to be located in distinct areas of the brain. This supports the idea that courtship conditioning results in two independent behavioral modifications: a decrement in courtship during the conditioning period and an associative memory of conditioning. This study has allowed us for the first time to genetically determine the circuit of information flow for a memory process in Drosophila. The map we have generated dissects the behavior into multiple components and will provide tools that allow both molecular and electrophysiological access to this circuit. (+info)
Statistical parametric mapping with 18F-dopa PET shows bilaterally reduced striatal and nigral dopaminergic function in early Parkinson's disease.
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OBJECTIVE: To apply statistical parametric mapping to 18F-dopa PET data sets, to examine the regional distribution of changes in dopaminergic metabolism in early asymmetric Parkinson's disease. METHODS: Thirteen normal volunteers (age 57.7 (SD 16.5) years; four women, nine men ) and six patients (age 50.3 (SD 13.5) years; three women, three men) with asymmetric (right sided) Parkinson's disease were studied. Images from each dynamic dopa PET dataset were aligned and parametric images of 18F-dopa influx (Ki) were created for each subject. The Ki images were transformed into standard stereotactic space. The Ki values of the caudate and putamen on spatially normalised images were compared with the Ki values before normalisation. The application of statistical parametric mapping (SPM) allowed statistical comparison of regional Ki values on a voxel by voxel basis between healthy volunteers and patients with Parkinson's disease. RESULTS: There was a strong correlation between the Ki values before and after spatial normalisation (r=0.898, p=0.0001). Significant decreases in the Ki values were found for the Parkinson's desease group throughout the entire left putamen (p< 0.001) and focally in the dorsal right putamen (p<0.001). Decreased Ki values were also shown bilaterally in the substantia nigra (p< 0.01). CONCLUSION: Using (SPM) and 18F-dopa PET, reductions in both striatal and nigral brain dopaminergic function could be demonstrated in early Parkinson's disease. (+info)
The roles of prefrontal brain regions in components of working memory: effects of memory load and individual differences.
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Using an event-related functional MRI design, we explored the relative roles of dorsal and ventral prefrontal cortex (PFC) regions during specific components (Encoding, Delay, Response) of a working memory task under different memory-load conditions. In a group analysis, effects of increased memory load were observed only in dorsal PFC in the encoding period. Activity was lateralized to the right hemisphere in the high but not the low memory-load condition. Individual analyses revealed variability in activation patterns across subjects. Regression analyses indicated that one source of variability was subjects' memory retrieval rate. It was observed that dorsal PFC plays a differentially greater role in information retrieval for slower subjects, possibly because of inefficient retrieval processes or a reduced quality of mnemonic representations. This study supports the idea that dorsal and ventral PFC play different roles in component processes of working memory. (+info)
Anatomical correlates of functional plasticity in mouse visual cortex.
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Much of what is known about activity-dependent plasticity comes from studies of the primary visual cortex and its inputs in higher mammals, but the molecular bases remain largely unknown. Similar functional plasticity takes place during a critical period in the visual cortex of the mouse, an animal in which genetic experiments can readily be performed to investigate the underlying molecular and cellular events. The experiments of this paper were directed toward understanding whether anatomical changes accompany functional plasticity in the developing visual cortex of the mouse, as they do in higher mammals. In normal mice, transneuronal label after an eye injection clearly delineated the monocular and binocular zones of area 17. Intrinsic signal optical imaging also showed monocular and binocular zones of area 17 but revealed no finer organization of ocular dominance or orientation selectivity. In normal animals, single geniculocortical afferents serving the contralateral eye showed great heterogeneity and no clustering consistent with the presence of ocular dominance patches. Growth and elaboration of terminal arbor continues beyond postnatal day 40 (P40), after the peak of the critical period. After prolonged monocular deprivation (MD) from P20 to P60, transneuronal labeling showed that the projection serving the ipsilateral eye was severely affected, whereas the effect on the contralateral eye's pathway was inconsistent. Optical imaging also showed profound effects of deprivation, particularly in the ipsilateral pathway, and microelectrode studies confirmed continued functional plasticity past P40. Reconstruction of single afferents showed that MD from P20 to P40 promoted the growth of the open eye's geniculocortical connections without causing the closed eye's contralateral projection to shrink, whereas MD from P20 to P60 caused an arrest of growth of deprived arbors. Our findings reveal numerous similarities between mouse and higher mammals in development and plasticity, along with some differences. We discuss the factors that may be responsible for these differences. (+info)
Spatiotemporal analysis of local field potentials and unit discharges in cat cerebral cortex during natural wake and sleep states.
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The electroencephalogram displays various oscillation patterns during wake and sleep states, but their spatiotemporal distribution is not completely known. Local field potentials (LFPs) and multiunits were recorded simultaneously in the cerebral cortex (areas 5-7) of naturally sleeping and awake cats. Slow-wave sleep (SWS) was characterized by oscillations in the slow (<1 Hz) and delta (1-4 Hz) frequency range. The high-amplitude slow-wave complexes consisted in a positivity of depth LFP, associated with neuronal silence, followed by a sharp LFP negativity, correlated with an increase of firing. This pattern was of remarkable spatiotemporal coherence, because silences and increased firing occurred simultaneously in units recorded within a 7 mm distance in the cortex. During wake and rapid-eye-movement (REM) sleep, single units fired tonically, whereas LFPs displayed low-amplitude fast activities with increased power in fast frequencies (15-75 Hz). In contrast with the widespread synchronization during SWS, fast oscillations during REM and wake periods were synchronized only within neighboring electrodes and small time windows (100-500 msec). This local synchrony occurred in an apparent irregular manner, both spatially and temporally. Brief periods (<1 sec) of fast oscillations were also present during SWS in between slow-wave complexes. During these brief periods, the spatial and temporal coherence, as well as the relation between units and LFPs, was identical to that of fast oscillations of wake or REM sleep. These results show that natural SWS in cats is characterized by slow-wave complexes, synchronized over large cortical territories, interleaved with brief periods of fast oscillations, characterized by local synchrony, and of characteristics similar to that of the sustained fast oscillations of activated states. (+info)
Electrophysiological and morphological evidence for a GABAergic nigrostriatal pathway.
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The electrophysiological and neurochemical characteristics of the nondopaminergic nigrostriatal (NO-DA) cells and their functional response to the degeneration of dopaminergic nigrostriatal (DA) cells were studied. Three different criteria were used to identify NO-DA cells: (1) antidromic response to striatal stimulation with an electrophysiological behavior (firing rate, interspike interval variability, and conduction velocity) different from that of DA cells; (2) retrograde labeling after striatal injection of HRP but showing immunonegativity for DA cell markers (tyrosine hydroxylase, calretinin, calbindin-D28k, and cholecystokinin); and (3) resistance to neurotoxic effect of 6-hydroxydomine (6-OHDA). Our results showed that under normal conditions, 5-8% of nigrostriatal neurons are immunoreactive for GABA, glutamic acid decarboxylase, and parvalbumin, markers of GABAergic neurons, a percentage that reached 81-84% after 6-OHDA injection. Electrophysiologically, NO-DA cells showed a behavior similar to that found in other nigral GABAergic (nigrothalamic) cells. In addition, the 6-OHDA degeneration of DA cells induced a modification of their electrophysiological pattern similar to that found in GABAergic nigrothalamic neurons. Taken together, the present data indicate the existence of a small GABAergic nigrostriatal pathway and suggest their involvement in the pathophysiology of Parkinson's disease. (+info)
Uneven mapping of magnocellular and parvocellular projections from the lateral geniculate nucleus to the striate cortex in the macaque monkey.
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Central vision is substantially over represented in the lateral geniculate nucleus (dLGN) and striate cortex. The over representation could be accompanied by a selective expansion of central vision in parvocellular dLGN, in which case the ratio of parvocellular to magnocellular inputs to striate cortex should change with retinal eccentricity. To test this, sample ratios were determined from counts of neurons in dLGN labelled retrogradely with WGA-HRP from striate cortex at the cortical representations of various eccentricities. Parvocellular to magnocellular ratios decreased from a mean of 35:1 at the fovea to 5:1 at 15 degrees eccentricity. Furthermore, they exceeded the ratio of P beta to P alpha ganglion cells in central retina, but not in peripheral retina, showing that the uneven P to M ratio in the LGN does not merely mirror the distribution of ganglion cells in the retina. This provides direct evidence for selective over representation of central vision in parvocellular dLGN. (+info)
Surgical treatment of intractable epilepsy originating from the primary sensory area of the hand--case report.
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A 14-year-old right-handed girl presented with intractable epilepsy originating from the primary sensory area of the hand, manifesting as sensory partial seizures in the left hand with secondary generalization. Neurological examination showed no abnormal findings. Magnetic resonance imaging, magnetoencephalography, and cortical stimulation using chronic subdural electrodes demonstrated a lesion located in the primary sensory cortex of the hand, in which the ictal onset zone was identified by 24-hour intracranial electroencephalographic recording. Surgical resection of the lesion and multiple subpial transections of the adjacent cortices were performed. The histological diagnosis was dysembryoplastic neuroepithelial tumor (DNT). She was completely free of seizures without permanent sensory deficits postoperatively. DNT located in the primary sensory hand area may be resectable without causing postoperative sensory deficits, if accurate functional mapping and surgical resection are performed. (+info)