Differential Expression of Two Glial Glutamate Transporters in the Rat Brain: an In Situ Hybridization Study (original) (raw)
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Chemical Senses, 1999
The purpose of the present study was to evaluate olfactory event-related potentials (OERPs) elicited by amyl acetate from subjects performing a visuomotor tracking task compared with the no-task conditions of eyes open and eyes closed. Task condition did not produce any reliable effects for any amplitude measure. Task type weakly influenced only P2 latency. Elder adults evinced smaller P2 and N1/P2 amplitudes and longer N1 and P2 latencies than young adults. The results suggest that tracking task performance is not necessary to obtain robust OERPs from normal subjects of a wide age range.
Olfactory event-related potentials and aging: normative data
International Journal of Psychophysiology, 2000
Ž Unlike the clinical usages of evoked potentials e.g. brain stem auditory evoked potentials for the assessment of . Ž. auditory function , normative data for the olfactory event-related potential OERP have been unavailable. The principal objective was to establish normative data across the human life span for OERPs with a given set of Ž parameters. Participants were 140 persons from seven age groups 16᎐19, 20᎐29, 30᎐39, 40᎐49, 50᎐59, 60᎐69 and . 70᎐79 years of age , with equal numbers of males and females, screened for nasal health and dementia. The odor stimulus was amyl acetate, presented at nasal temperature in a humidified airstream delivered by an air-dilution olfactometer at a constant flow rate, using a 60-s inter-stimulus interval. OERPs were recorded at Fz, Cz, and Pz electrode sites, amplified and averaged over trials. Amplitudes of the N1rP2 and P3 and latencies of the P2 and P3 Ž . were analyzed. Processing speed decreased at a constant rate over decades for the sensory P2 latency as well as Ž . cognitive P3 latency components. Decline in amplitude over decades was also apparent. Normative data will be useful in research on olfactory function and in clinical assessment of olfactory functional status. ᮊ
Chemical senses, 2018
A widely held view is that top-down modulation of sensory information relies on an amodal control network that acts through the thalamus to regulate incoming signals. Olfaction lacks a direct thalamic projection, which suggests that it may differ from other modalities in this regard. We investigated the late positive complex (LPC) amplitudes of event-related potentials (ERP) from 28 participants, elicited by intensity-matched olfactory, auditory and visual stimuli, during a condition of focused attention, a neutral condition, and a condition in which stimuli were to be actively ignored. Amplitudes were largest during the attend condition, lowest during the ignore condition, with the neutral condition in between. A Bayesian analysis resulted in strong evidence for similar effects of task across sensory modalities. We conclude that olfaction, despite its unique neural projections, does not differ from audition and vision in terms of task-dependent neural modulation of the LPC.
Neuroscience, 2009
Olfactory disorders are common in patients with idiopathic Parkinson's disease (IPD). In IPD patients with hyposmia olfactory event-related potentials (ERPs) are typically found to be delayed or absent. Altered ERPs in IPD patients may also be consistent with reduced neuronal activity in the medial temporal lobe following olfactory stimulation, as demonstrated by functional magnetic resonance imaging (fMRI). We analyzed ERPs and fMRI scans of hyposmic IPD patients (n)81؍ to gain further insight about the brain regions involved in generation of olfactory ERPs. Patients were separated into two groups (n9؍ per group), based on the detectability (؉) or non-detectability (؊) of ERPs. Central activation during olfactory stimulation was examined using fMRI. Both ERP؉ and ERP؊ patients showed activity in brain areas relevant to olfactory processing, such as the amygdala, parahippocampal regions, and temporal regions (BA 37, 21/ 22). Comparison of both groups revealed higher activation in ERP؉ patients, especially in the amygdala, parahippocampal cortex, inferior frontal gyrus (BA 47), insula, cingulate gyrus, striatum, and inferior temporal gyrus. The relationship between the expression of olfactory ERPs and cortical activation patterns seen during olfactory stimulation in fMRI in IPD patients supports the idea that ERPs are a sensitive marker of neurodegeneration in olfactory regions. In accordance with current neuropathological staging concepts, olfactory ERPs may be reflecting pathological changes in olfactory regions, independent of the typically observed nigro-striatal degeneration in IPD. Reduced activation of primary olfactory areas in the ERP-group may reflect a severe disruption of olfactory processing in these patients.
Functional Significance of Olfactory-induced Oscillations in the Human Amygdala
Cerebral Cortex, 2005
We recorded directly from the amygdalar nucleus of nine epileptic patients performing a delayed odor-matching recognition memory task. Time--frequency analysis of the responses to the odorants revealed that the stimulations elicited induced oscillatory responses, as well as already described olfactory evoked potentials. These oscillatory responses were composed of two frequency components -one in the beta band (15--25 Hz) and a faster one, in the low gamma band (25--35 Hz) -both of which lasted during the full duration of the inspiration. In pairs of identical odorants, the power of gamma oscillations was weaker for the second odorant (the target) than for the first one (the sample). We observed no such difference when the first and second odorants of a pair were different. Thus, gamma oscillations in the amygdala are weaker for repeated stimuli, a mechanism known as repetition suppression. This is consistent with an involvement of the human amygdala in the encoding and retrieval of olfactory information independently of its hedonic properties, at least in epileptic patients. Altogether, our results corroborate in humans evidence found in animals that oscillations serve as a common coding process of olfactory information.
Assessment and Scientific Progresses in the Analysis of Olfactory Evoked Potentials
Bioengineering
The human sense of smell is important for many vital functions, but with the current state of the art, there is a lack of objective and non-invasive methods for smell disorder diagnostics. In recent years, increasing attention is being paid to olfactory event-related potentials (OERPs) of the brain, as a viable tool for the objective assessment of olfactory dysfunctions. The aim of this review is to describe the main features of OERPs signals, the most widely used recording and processing techniques, and the scientific progress and relevance in the use of OERPs in many important application fields. In particular, the innovative role of OERPs is exploited in olfactory disorders that can influence emotions and personality or can be potential indicators of the onset or progression of neurological disorders. For all these reasons, this review presents and analyzes the latest scientific results and future challenges in the use of OERPs signals as an attractive solution for the objective ...
Olfactory pathway evoked potentials in response to hypothalamic stimulation
Brain Research Bulletin, 1978
Olfactory pathway evoked potentinls in response to hypofhukunic stimulation. BRAIN RES. BULL. 3(S) 467-474, 1978.-Ipsilateral and contralateral stimulation of lateral, ventromedial and posterior hypothalamic nuclei produced evoked responses in the olfactory bulb and in the prepyriform cortex. No differences in the latencies were found by stimulation of each nucleus in the homo and contralateral olfactory structures. The high amplitude of the fast component (Nl) was obtained with stimuli applied to the ventral zones and the slow components (N2,N3) were obtained with more dorsal stimulation. An ipsilatetal pathway is indicated at the supramammillary and posterior commissure level, since severing these structures abo!ishes the evoked responses. A bilateral projection is proposed for the olfactory bulb. Evoked potentials Olfactory system Centrifugal fibers Olfactory bulb Prepyriform cortex EFFERENT fibers to the olfactory system have been extensively investigated
2006
Functional imaging signals arise from metabolic and hemodynamic activity, but how these processes are related to the synaptic and electrical activity of neurons is not well understood. To provide insight into this issue, we used in vivo imaging and simultaneous local pharmacology to study how sensory-evoked neural activity leads to intrinsic optical signals (IOS) in the well-defined circuitry of the olfactory glomerulus. Odorevoked IOS were tightly coupled to release of glutamate and were strongly modulated by activation of presynaptic dopamine and GABA-B receptors. Surprisingly, IOS were independent of postsynaptic transmission through ionotropic or metabotropic glutamate receptors, but instead were inhibited when uptake by astrocytic glutamate transporters was blocked. These data suggest that presynaptic glutamate release and uptake by astrocytes form a critical pathway through which neural activity is linked to metabolic processing and hence to functional imaging signals.