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PubMed1993

Effects of vasoactive intestinal polypeptide on the response properties of cells in area 17 of the cat visual cortex.

1. Vasoactive intestinal polypeptide (VIP) was iontophoretically applied to a population of 90 single cells in the primary visual cortex (area 17) of the cat. Response magnitude, response selectivity, spontaneous activity, and the ratio between the visual response and spontaneous activity (signal-to-noise ratio) of the cells were assessed quantitatively before and during drug application. 2. VIP had little effect in the absence of visual stimulation, with only 29/90 (32%) of the cells showing a change of even 1 sp/s in their spontaneous activity. In contrast it had a clear effect on the visual responses of the majority (73/90, 81%) of the cells tested. 3. VIP produced a substantial change (i.e., > or = 40%) in optimal response magnitude for 57 of the affected cells. Of these 65% were facilitated, usually with no change or an improvement in signal-to-noise ratio and direction selectivity. The remaining cells were inhibited, with more variable effects on their visual response characteristics, and were found predominantly in the superficial laminae. 4. The effects of VIP bore a remarkable resemblance to those reported previously for the muscarinic action of acetylcholine (ACh). VIP and a muscarinic cholinergic agonist, either ACh or acetyl-beta-methacholine (MeCh), were therefore applied in turn to a group of 40 cells. In 23 cases VIP and the muscarinic agonist were also applied simultaneously. 5. The effects of VIP and the cholinergic agonist matched in 92% of the cases where both drugs were effective. That is to say, cells that were facilitated by VIP were facilitated also by ACh or MeCh, and vice versa. In many instances there was a clear similarity in the pattern as well as the direction of the effects produced by the two substances. The result of simultaneous application was generally additive. 6. These data suggest that VIP and ACh activate very similar postsynaptic mechanisms, and share a closely related function at the level of individual cortical cells. Thus VIP may facilitate the responses of both the excitatory and the inhibitory components of the cortical circuit, leading to an overall increase in responsiveness and selectivity. In contrast to the cholinergic input from the basal forebrain, however, the VIP-positive cortical cells are likely to exert a very localized influence, over a circumscribed region of the cortex, in response to the presence of an effective visual stimulus.

Acetylcholine↗
PubMed1984

Anatomy and physiology of a color system in the primate visual cortex.

Staining for the mitochondrial enzyme cytochrome oxidase reveals an array of dense regions (blobs) in the primate primary visual cortex. They are most obvious in the upper layers, 2 and 3, but can also be seen in layers 4B, 5, and 6, in register with the blobs in layers 2 and 3. We compared cells inside and outside blobs in macaque and squirrel monkeys, looking at their physiological responses and anatomical connections. Cells within blobs did not show orientation selectivity, whereas cells between blobs were highly orientation selective. Receptive fields of blob cells had circular symmetry and were of three main types, Broad-Band Center-Surround, Red-Green Double-Opponent, and Yellow-Blue Double-Opponent. Double-Opponent cells responded poorly or not at all to white light in any form, or to diffuse light at any wavelength. In contrast to blob cells, none of the cells recorded in layer 4C beta were Double-Opponent: like the majority of cells in the parvocellular geniculate layers, they were either Broad-Band or Color-Opponent Center-Surround, e.g., red-on-center green-off-surround. To our surprise cells in layer 4C alpha were orientation selective. In tangential penetrations throughout layers 2 and 3, optium orientation, when plotted against electrode position, formed long, regular, usually linear sequences, which were interrupted but not perturbed by the blobs. Staining area 18 for cytochrome oxidase reveals a series of alternating wide and narrow dense stripes, separated by paler interstripes. After small injections of horseradish peroxidase into area 18, we saw a precise set of connections from the blobs in area 17 to thin stripes in area 18, and from the interblob regions in area 17 to interstripes in area 18. Specific reciprocal connections also ran from thin stripes to blobs and from interstripes to interblobs. We have not yet determined the area 17 connections to thick stripes in area 18. In addition, within area 18 there are stripe-to-stripe and interstripe-to-interstripe intrinsic connections. These results suggest that a system involved in the processing of color information, especially color-spatial interactions, runs parallel to and separate from the orientation-specific system. Color, encoded in three coordinates by the major blob cell types, red-green, yellow-blue, and black-white, can be transformed into the three coordinates, red, green, and blue, of the Retinex algorithm of Land.

Animals↗
PubMed2005

Influence of gradient acoustic noise on fMRI response in the human visual cortex.

A paired-stimuli paradigm combined with fMRI was utilized to study the effect of gradient acoustic noise on fMRI response in the human primary visual cortex (V1) in terms of the auditory-visual cross-modal neural interaction. The gradient noise generated during the fMRI acquisition was used as the primary stimulus, and a single flashing light was used as the secondary stimulus. An interstimulus interval (ISI) separated the two. Six tasks were designed with different ISIs ranging from 50 to 700 ms. Both BOLD signal intensity and the number of activated pixels in V1 were analyzed and examined, and they showed a significant reduction when the gradient noise preceded the flashing light by approximately 300 ms. These results indicate that the gradient acoustic noise generated during fMRI acquisitions does interfere with neural behavior and the BOLD signal in the human visual cortex. This interference is modulated by the delay between the gradient noise and visual stimulation, and it can be studied quantitatively when the stimulation paradigm is designed appropriately. This study provides evidence of the auditory-visual interaction during fMRI studies, and the results should have an impact on fMRI applications.

Acoustics↗
PubMed1998

Brain mapping with single photon emission CT.

PURPOSE: To investigate the feasibility of performing brain mapping studies by using cortical activation paradigms and single photon emission computed tomography (SPECT) and to evaluate methods of analysis. MATERIALS AND METHODS: Twenty healthy volunteers underwent technetium-99m bicisate SPECT under baseline conditions and during either full-field or right hemifield visual stimulation with a black and white reversing checkerboard pattern. Changes in regional cerebral perfusion were measured by using regions of interest (ROIs) and statistical parametric mapping. RESULTS: ROI analysis identified statistically significant increases in perfusion in the occipital cortex with full-field visual stimulation (mean +/- standard error of the mean percentage change from baseline: left, 8.0 +/- 1.5; right, 6.6 +/- 2.4). With right hemifield visual stimulation, perfusion was significantly increased only in the left occipital cortex (left, 5.2 +/- 1.5; right, -0.2 +/- 1.9). Statistical parametric mapping showed areas of activation (more than 100 voxel clusters showed significant change from baseline at a threshold value of P < or = .005 or z > or = 2.58) in the left primary visual cortex (right hemifield visual stimulation) and in both right and left primary visual areas (full-field visual stimulation). CONCLUSION: Brain mapping studies were preformed with Tc-99m bicisate SPECT, and activation-induced changes were visualized and measured. These methods can be applied to develop improved methods of diagnosis and assessment of treatment outcome in patients with neuropsychiatric disorders.

Adult↗
PubMed2005

A stereoscopic look at visual cortex.

Three recent studies offer new insights into the way visual cortex handles binocular disparity signals. Two of these studies recorded from single neurons in two different visual areas of the monkey brain, one (V5/MT) in dorsal and one (V4) in ventral cortex. While V5/MT neurons respond similarly to neurons in primary visual cortex (V1), V4 neurons appear to reflect a more advanced stage in the analysis of retinal disparity, closer to the perceptual experience of stereoscopic depth. Both studies are consistent with a third study using fMRI to address similar questions in humans. Together with previous evidence, these results suggest a new framework for understanding stereoscopic processing based on the separation between ventral and dorsal streams in visual cortex.

Animals↗
PubMed1987

Regional heterogeneity in the distribution of somatostatin-28- and somatostatin-28(1-12)-immunoreactive profiles in monkey neocortex.

The distribution of the prosomatostatin-derived peptides (PSDP), somatostatin-28 and somatostatin-28(1-12), in the cynomolgus monkey (Macaca fascicularis) neocortex was characterized in quantitative immunohistochemical studies of 3 visual areas (V1, primary visual cortex; V2, the adjacent visual association area; and AIT, a visual association area in anterior inferior temporal cortex), 2 auditory areas (AI, primary auditory cortex; and T1, an adjacent auditory association area) and anterior cingulate cortex (Area 24). The results of similar quantitative analyses in 3 homologous areas in rat neocortex (primary visual, primary auditory, and anterior cingulate) are also presented. Primate cortical areas differed significantly in both density and laminar distribution of PSDP-immunoreactive profiles. Area 24, the most densely labeled area, had nearly 6 times as many PSDP-immunoreactive neurons as V1. Both auditory areas contained approximately two-thirds the number of PSDP-immunoreactive neurons found in Area 24; however, both had nearly 4 times as many immunoreactive neurons as V1. The 3 visual areas showed incremental increases in the number of PSDP-immunoreactive neurons; V2 contained nearly twice and AIT nearly 3 times the number of immunoreactive neurons present in V1. Both the supra- and infragranular layers were densely labeled in Area 24 and Area T1, however, in AI, V1, V2, and AIT the infragranular layers were relatively sparsely labeled. In contrast to the regional heterogeneity found in the primate neocortex, the distribution of immunoreactive neurons was quite uniform across the 3 rat cortical areas. The rat cortical areas contained substantially fewer immunoreactive neurons than most of the monkey cortical areas, and a majority of these immunoreactive neurons were located in the infragranular layers. These findings suggest that the regional specialization of primate neocortex involves the selective distribution of PSDP-immunoreactive neurons. They also suggest that chemically specified intrinsic organization of neocortex is not likely to be uniform across species or across cortical areas in the primate. The distinctive regional distribution patterns of PSDP-immunoreactive profiles appear to parallel that of the long corticocortical projections (contralateral and distant ipsilateral projections), suggesting an association between these presumed inhibitory interneurons and this important extrinsic system.

Animals↗
PubMed1996

Global plasticity in adult visual cortex following reversal of visual input.

The reversal or displacement of the retinal image by prism spectacles leads to extreme disruption of visually guided behaviour, but after an extended period of visual transformation normal behaviour is gradually restored. It is unclear whether this adaptation involves a change in visual perception, the learning of new motor responses, a modification of the sensori-motor control system or a proprioceptive change in the perceived positions of the body parts. Here I describe the effects of visual field reversal on neuronal activity in the monkey visual cortex. After a few months of wearing reversing spectacles, some cells in the primary visual cortex began to respond to stimuli presented not only in the contralateral visual field but also in the ipsilateral field. These cells were not selective for orientation or direction of motion, but responded well to a light flash. This result suggests that adaptation to visual field reversal is mediated, at least in part, by a large-scale functional reorganization at an early stage in the visual processing pathway.

Adaptation, Physiological↗
PubMed1992

The effects of dark-rearing on the electrophysiology of the rat visual cortex.

Our previous two studies have shown that dark-rearing affects the morphology and chemistry of adult rat primary visual cortex (area 17). In this study we demonstrate correlated physiological alterations with single unit recordings in the same preparation. Rats were raised from birth in either 14 h light/10 h dark (Lt/Dk) or in total darkness (Dk). At the age of 3 months, single units were recorded in area 17 of both groups. The cortical cells of Dk animals showed significantly more spontaneous activity during ambient lighting. The mean rate of randomly appearing spontaneous activity was greatly increased in Dk animals. Moreover, many cells in Dk animals also exhibited a particular type of spontaneous activity which occurred as 'bursts' of spikes, i.e. quantified groupings of fast firing spikes, separated by randomly appearing spontaneous activity. The mean number of bursts per min seen in Dk animals was also significantly more than any such activity seen in Lt/Dk animals. Visual stimuli consisted of white or dark bars moving with different orientations and directions at slow and fast speeds, and full field flashes. In response to moving stimuli, notably fewer cells were orientation- or direction tuned in dark-reared animals, and when they did respond to moving bar stimuli, the responses were of relatively longer duration. The pathologically high spontaneous activity rate, as well as lack of tuning and relatively prolonged duration of responses to moving stimuli indicate that intracortical inhibitory mechanisms are seriously compromised in both the unstimulated and stimulated states and is in agreement with our previous findings (Bakkum, B.W., Port, J.D., Cohen, R.S. and Benevento, L.A., Soc. Neursci. Abst., 15 (1989) 797) of a decreased number of synapses and GABA-containing cells in the visual cortex of the same preparation. Other evidence suggests that there may be a decrease in stimulus-bound excitatory drive. Significantly fewer cells in Dk animals were excited by all visual stimuli, and responses elicited by flashes had relatively longer 'on' latencies, relatively shorter durations, and were generally weaker. This may correlate with our finding of a significantly smaller number of perforated postsynaptic densities in the cortex of the same preparation (Bakkum, B.W., Benevento, L.A. and Cohen, R.S., J. Neurosci. Res., 23 (1991) 65-80).

Action Potentials↗
PubMed1993

Development of local horizontal interactions in cat visual cortex studied by cross-correlation analysis.

1. To explore the functional development of local horizontal interactions in the primary visual cortex, we carried out cross-correlation analysis of spike trains recorded simultaneously from a pair of neurons separated horizontally by < 1 mm, in kittens ranging in age postnatally from the second to ninth week. 2. Significantly correlated firings were found in 87 pairs of cells among 423 pairs analyzed, and 77 pairs of them were classified into three types on the basis of their functional implications: 1) excitatory interactions, 2) inhibitory interactions, and 3) common inputs to both neurons of the pair from other sources. 3. Common inputs and excitatory linkage were observed even in animals at the second postnatal week, whereas inhibitory linkage was not seen before the fourth week of age. The probability of observing common inputs and inhibitory linkage increased during development, whereas that of excitatory linkage tended to decrease after the sixth week of age. 4. Significant correlation was rarely seen in pairs with horizontal separation > 600 microns in the seventh to ninth week. In the fourth to sixth week of age, however, approximately 30% of the pairs with horizontal separation between 600 and 800 microns were significantly correlated. 5. Cells that were not sensitive for orientation or that lacked a visual response were observed mainly before the sixth week of age. These cells tended to receive excitatory effects from and share common inputs with other orientation-sensitive cells that were located within the horizontal distance of 400 microns. 6. All three types of correlations were observed mostly in cell pairs with preferred orientations that differed < 45 degrees at all ages studied. In the fourth to sixth week, however, the similarity of orientation preference was not strict, and correlated firings were observed even in a pair with orthogonal orientation preferences; whereas in the seventh to ninth week the tuning became sharper. 7. These results suggest that functional interactions between cortical neurons exist but are much less specific with respect to horizontal separation and orientation preference before the sixth week of age, and these interactions become more specific so as to operate between neurons with similar orientation preferences in more restricted region after the seventh to ninth week of age and thus in adulthood.

Aging↗
PubMed1987

Local circuitry of identified projection neurons in cat visual cortex brain slices.

The relationship between pyramidal cell morphology and efferent target was investigated in layer 6 of cat primary visual cortex (area 17). Layer 6 has 2 projections, one to the lateral geniculate nucleus (LGN) and another to the visual claustrum. The cells of origin of each projection were identified by retrograde transport of fluorescent latex microspheres. The labeled cells were visualized in brain slices prepared from area 17, using an epifluorescence compound microscope modified for intracellular recording. Individual retrogradely labeled cells were penetrated and intracellularly stained with Lucifer yellow to visualize the patterns of axons and dendrites associated with each projection. The neurons that give rise to the 2 projections had very different patterns of dendrites and local axonal collaterals, but the patterns within each group were highly stereotyped. The differences between their axonal collaterals were particularly dramatic. Claustrum projecting cells had fine, horizontally directed collaterals that arborized exclusively in layer 6 and lower layer 5. Most LGN projecting cells had virtually no horizontal arborization in layer 6. Instead, they sent widespread collaterals vertically, which arborized extensively in layer 4. The apical dendrites of the 2 groups also differed markedly. Claustrum projecting cells had apical dendrites reaching to layer 1, with branches in layer 5 only, while LGN projecting cells never had an apical dendrite reaching higher than layer 3, with side branches in layers 5 and 4. Therefore, each efferent target must receive inputs from neurons whose synaptic connections within area 17 are significantly different from those of neurons projecting to other targets. This further suggests that distinct visual response properties should be associated with each projection. In addition to the claustrum and LGN projecting cells, about 20% of layer 6 pyramidal neurons lacked an efferent axon. Morphologically, most resembled LGN projecting neurons, but a few had characteristics of claustrum projecting cells. These neurons may represent cells that either failed to make an efferent connection or cells that lost an efferent axon during development. Their frequency suggests that such intrinsic, presumably excitatory, neurons may play a significant role in cortical processing.

Animals↗
PubMed1982

Receptive fields of neurons in the cats visual cortex after a change of alertness level.

Exact and reliable changes in receptive fields (RF) of neurons in the primary visual cortex were revealed after the action of extravisual stimuli such as air-puff to the corner of a closed eye which leads to an enhancement of alertness level. Such stimulus evoked a change in the configuration and size of RFs in most investigated units. This lasted from 15 to 30 min and in most cases the size of RFs excitatory zones decreased, while the size of inhibitory surround increased. This effect could be seen at different levels of visual adaptation. Under light and short anesthesia (sombrevin) the main picture of RF change was different: increase of excitatory zones and nearly equal probability of the opposite changes in inhibitory RF parts lasting from 5 to 30 min. The role of intracortical inhibitory systems in the modulation of RF size and form is discussed. The possible behavioral meaning of the observed effects may consist in the fine description of signal properties in the small RFs at high alertness level, while under opposite conditions enlarged RFs can serve to improve signal detection and organization of orienting reaction even to a weak new stimulus.

Animals↗
PubMed2004

Visual functional magnetic resonance imaging in patients with Sturge-Weber syndrome.

The purpose of this study is to report different patterns of visual cortex activation in patients with Sturge-Weber syndrome as compared with healthy control subjects. Utilizing a visual paradigm of flashing lights, three children with Sturge-Weber syndrome were studied with functional magnetic resonance imaging. The results are compared with those documented in eight normal sedated children, and six young adult awake volunteers, using the same paradigms. All adult volunteers manifested bilateral activation in primary visual cortex (Brodmann's 17 and 18 areas). Two of them also had activation in secondary visual cortex (Brodmann's 19 area). In the eight sedated normal children, seven manifested activation in primary visual areas. The last exhibited no activation. The patients with Sturge-Weber syndrome demonstrated in the affected occipital lobe increased activation in one patient (11 months old), no activation in the second (12 years of age), and abnormal distribution of the activation in the third (11 months old). This report demonstrates that the vascular malformation of Sturge-Weber syndrome does not necessarily prevent cortical activation in the expected occipital cortex and may be associated with different patterns of abnormal activation. Assessing cortical function with functional magnetic resonance imaging in patients with Sturge-Weber syndrome may be helpful in decisions of surgical management and counseling.

Adolescent↗
PubMed2001

Perinatal-lesion-induced reorganization of cerebral functions revealed using reversible cooling deactivation and attentional tasks.

We tested the concept that lesions of primary visual cortical areas 17 and 18 sustained on the day of birth induce a redistribution of cerebral operations underlying the ability to disengage visual attention and then redirect it to a new location. In cats, these operations are normally highly localizable to posterior middle suprasylvian (pMS) cortex. Three stimulation paradigms were used: (i) movement of a high contrast visual stimulus into the visual field; (ii) illumination of a static light-emitting diode (LED) stimulus; and (iii) a control static auditory stimulus. To test for the redistribution of critical neural operations, cryoloops were implanted bilaterally in the pMS sulcus and in contact with ventral posterior suprasylvian (vPS) cortex. Separate and combined deactivations of pMS and vPS cortices in cats with early lesions of primary visual cortex showed that full, unilateral deactivation of pMS cortex only partially impaired the ability to detect and orient to stimuli moved into the contracooled hemifield. Much more complete impairment required the additional deactivation of ipsilateral vPS cortex. Bilateral pMS deactivation alone, or in combination with bilateral vPS deactivation, largely reversed the unilateral contracooled neglect. For the orienting to static, illuminated LED stimuli, unilateral deactivation of pMS cortex was sufficient to fully impair orienting to stimuli presented in the contracooled hemifield. Bilateral pMS deactivation induced an almost complete visual-field-wide neglect of stimuli. On its own, unilateral deactivation of vPS cortex was without effect on either task, although bilateral vPS deactivations introduced inconsistencies into the performance. Termination of cooling reversed all deficits. Finally, neither the initial lesion of areas 17 and 18 nor cooling of either the MS or vPS cortex alone, or in combination, interfered with orienting to sound stimuli. Overall, our results provide evidence that at least one highly localizable visual function of normal cerebral cortex is remapped across the cortical surface following the early lesion of primary visual cortical areas 17 and 18. Moreover, the redistribution has spread the essential neural operations from the visual parietal cortex to a normally functionally distinct type of cortex in the visual temporal system.

Acoustic Stimulation↗
PubMed2005

Columnar organization of the mammalian visual cortex and its vulnerability following lesion in adult cats.

It is well known that in the mammalian visual cortex the neurons, sharing similar response properties, are grouped together into functional units, known as cortical columns. The orientation and ocular dominance columnar organization is a fundamental element for both the anatomical and physiological features of the visual cortex. Nonetheless, little is known about the functional restoration of matured columnar columns following injury. In the present study, the visual cortex of adult cats was studied electrophysiologically, whereas the primary goal of the study was to reveal the functional stability of the columns, disconnected from the main visual input. Experiments were performed on the primary visual cortex (area 17) of 13 anaesthetized and paralyzed adult cats. The columnar distortion was produced by surgical incision perpendicular to the cortical columns. The single unit activity was recorded from 1186 visual cells (experimental groups) in areas proximal and distal to the lesion and, compared to data, received from intact visual cortex (control group). The results indicate that most of the visually responsive cells were found to be selective to specific orientation in all experimental groups (75-100%) similar to the normal control group (78%). Moreover, the distribution of orientation-specific cells was very similar in all experimental and control groups (p > 0.05), as well as in both recording areas (p > 0.05). The percentage of binocular cells was significantly lower in all experimental groups (23-49%) in comparison to the control (80%). However, the distribution of the binocular cells revealed the significant similarity between the experimental and control groups (p > 0.05). An additional finding of the study is that the visual responsiveness of cells was significantly reduced in all experimental groups: only 28-49% of cells were found to be responsive following injury, as compared to 86% in normal control group (p < 0.001). The distribution of cells has also been analysed in accordance with their directional specificity and it has been found that the majority of cells in the experimental groups were found to be bias and non-specific to light stimuli (52-84%) as compared normal controls (21%) (p < 0.001). It has been concluded that, despite the fact that no improvement in visual function was found, the inherent structure of the disrupted cortical columns in the visual cortex was generally preserved. Therefore, the disruption of the columnar connection does not lead to remarkable distortion of the connectivity pattern on the whole, though it does reduce the responsiveness level there. It was concluded that the columnar structure for both orientation and ocular dominance is characterized by high stability, which enables visual processing with minimal brain connections.

Animals↗
PubMed2005

Spontaneously emerging direction selectivity maps in visual cortex through STDP.

It is still an open question as to whether, and how, direction-selective neuronal responses in primary visual cortex are generated by feedforward thalamocortical or recurrent intracortical connections, or a combination of both. Here we present an investigation that concentrates on and, only for the sake of simplicity, restricts itself to intracortical circuits, in particular, with respect to the developmental aspects of direction selectivity through spike-timing-dependent synaptic plasticity. We show that directional responses can emerge in a recurrent network model of visual cortex with spiking neurons that integrate inputs mainly from a particular direction, thus giving rise to an asymmetrically shaped receptive field. A moving stimulus that enters the receptive field from this (preferred) direction will activate a neuron most strongly because of the increased number and/or strength of inputs from this direction and since delayed isotropic inhibition will neither overlap with, nor cancel excitation, as would be the case for other stimulus directions. It is demonstrated how direction-selective responses result from spatial asymmetries in the distribution of synaptic contacts or weights of inputs delivered to a neuron by slowly conducting intracortical axonal delay lines. By means of spike-timing-dependent synaptic plasticity with an asymmetric learning window this kind of coupling asymmetry develops naturally in a recurrent network of stochastically spiking neurons in a scenario where the neurons are activated by unidirectionally moving bar stimuli and even when only intrinsic spontaneous activity drives the learning process. We also present simulation results to show the ability of this model to produce direction preference maps similar to experimental findings.

Models, Neurological↗
PubMed2005

Imaging monetary reward in pathological gamblers.

We acquired two 18F-deoxyglucose positron emisssion tomography (PET) scans on seven unmedicated pathological gamblers, at least 7 days apart. Following an injection of 5 mCi FDG, subjects carried out a computer blackjack task for 35 min under two different reward conditions: monetary reward and computer game points only. Relative FDG metabolic rate was obtained from regions of interest in the prefrontal cortex, cingulate, striatum and visual cortex. Monetary reward blackjack was associated with significantly higher relative metabolic rate in the primary visual cortex (Brodmann area 17), the cingulate gryus (Brodmann area 24), the putamen and prefrontal areas 47 and 10, compared to blackjack playing for points only. No area tested showed a significant decrease. This pattern suggests heightened limbic and sensory activation in the gambling for money condition with increased emotional valence and greater risk and reward, and confirms the salience of monetary reward in the development of pathological gambling.

Adult↗
PubMed2006

Neural effects of MDMA as determined by functional magnetic resonance imaging and magnetic resonance spectroscopy in awake marmoset monkeys.

We used functional magnetic resonance imaging (fMRI) to investigate the acute effects of a recreational dose (1 mg/kg p.o.) of 3,4-methylenedioxymethamphetamine (MDMA) on regional brain activity in awake, restrained marmoset monkeys. In a second study, magnetic resonance spectroscopy (MRS) and postmortem measurements of serotonin transporter (SERT) binding and serotonin (5-HT) concentrations were used to determine the neurotoxic effects of low (4 x 1 mg/kg p.o.) and high (4 x 10 mg/kg i.m.) doses of MDMA. Several brain areas were significantly activated by the low oral dose of MDMA, including the midbrain raphe nuclei, hippocampus, hypothalamus, amygdala, and the corticostriatal circuit composed of the dorsal thalamus, sensory motor cortex, and basal ganglia. MDMA activated the primary visual cortex under baseline conditions and also enhanced the visual cortical response to photic stimulation. The onset of brain activation correlated well with the rise in plasma MDMA concentrations measured in separate monkeys given the same drug treatment. In the second study, the ratio of N-acetylaspartate (NAA; a putative neuronal marker) to creatine was significantly reduced in the hypothalamus following either MDMA treatment regimen, suggesting a particular vulnerability of this structure to MDMA-induced damage. Monkeys given the high-dose regimen also showed prolonged hyperthermia and reductions in 5-HT and SERT in a number of brain areas. These results are the first to identify the pattern of MDMA-induced brain activation in a nonhuman primate model, and they further suggest that even recreational doses of MDMA may have adverse consequences as indicated by the reduced hypothalamic NAA/creatine ratio.

Animals↗