Topographic Brain Maps Research Articles

Decoding Imagined Speech from EEG Data: A Hybrid Deep Learning Approach to Capturing Spatial and Temporal Features.

Neuroimaging is revolutionizing our ability to investigate the brain's structural and functional properties, enabling us to visualize brain activity during diverse mental processes and actions. One of the most widely used neuroimaging techniques is electroencephalography (EEG), which records electrical activity from the brain using electrodes positioned on the scalp. EEG signals capture both spatial (brain region) and temporal (time-based) data. While a high temporal resolution is achievable with EEG, spatial resolution is comparatively limited. Consequently, capturing both spatial and temporal information from EEG data to recognize mental activities remains challenging. In this paper, we represent spatial and temporal information obtained from EEG signals by transforming EEG data into sequential topographic brain maps. We then apply hybrid deep learning models to capture the spatiotemporal features of the EEG topographic images and classify imagined English words. The hybrid framework utilizes a sequential combination of three-dimensional convolutional neural networks (3DCNNs) and recurrent neural networks (RNNs). The experimental results reveal the effectiveness of the proposed approach, achieving an average accuracy of 77.8% in identifying imagined English speech.

Paula Muhr, From Photography to FMRI: Epistemic Functions of Images in Medical Research on Hysteria

This is an important book on the epistemic role of images in the production of knowledge about hysteria during the last three decades of the nineteenth century and the first two of the twenty-first century. Muhr successfully shows the commonalities between the operationalisation of visualisations in Jean-Martin Charcot’s work and present-day functional magnetic resonance imaging (fMRI)-based hysteria research. The author offers an analysis of the operative meanings of images as opposed to a more classical iconographic examination. The book reviews the various types of images that have been used in medical research settings in two critical moments of history that, as Muhr notes, have reshaped our current understanding of hysteria. The first chapter makes a case for the possibility that images were instrumental to Charcot as epistemic tools rather than mere graphic representations. From a knowledge perspective, there is much unsaid about the actual role of visualisations in the conceptualisation of hysteria. Images, Muhr explains, are sources of information about the bodies and brains of those deemed to suffer from a condition, as difficult to determine as hysteria is. Iconographic surveys risk overlooking the epistemic value of images for the trained eye. For Charcot, images were an integral part of a knowledge production apparatus. Interpretation was also linked to the medium in question. Besides photographs, Charcot’s toolbox included body maps, diagrams, line graphs, myographic and pneumographic curves, schematic drawings, sketches and topographic brain maps. None of which were used in isolation. They allowed for the type of detailed observation that could inform medically operative meanings. Until a century-long hiatus would ensue. Images seem to have disappeared from hysteria research contexts. Muhr continues in the second chapter by contextualising the reappearance of images as tools in the systematic study of a ‘still unknown brain dysfunction’ (p. 257) in the twenty-first century.

Unique Medium Chain Triglyceride Product Rapidly Enhances Brain Function: A Pilot Investigational Study

PURPOSE: Medium Chain Triglyceride (MCT) compounds are purported to increase brain energy based upon the relationship between MCT products and ketone production, especially for older individuals or those on low-carbohydrate diets. Little evidence exists that MCT products positively affect brain function, short-term. In this pilot study, Intervention Group (IG )subjects were tested prior to ingestion of a proprietary MCT product, and then 90 minutes later using the same electro-encephalographic (EEG) device and compared to a control group (CG). METHODS: Eight (8) IG volunteers, aged 49-68 years old, (male = 5, female =3) were compared to three (3) CG volunteers, aged 48 to 68 years old, (male = 3). Study subjects completed standard EEG testing prior to ingestion of the compound, and 90 minutes after consuming the compound or placebo. Testing consisted of a P300 audio reaction time test and two visual decision making/reaction tests. RESULTS: The IG increased brain function as measured with evoke potentials, time to task and graphic representations compared to the control group. The decrease for the IG in the audio reaction time test was 340 milliseconds to 314 milliseconds. In addition, the tens of millivolt (μV) activation during the auditory reaction time test increased from 7.5 μV to 12.9 μV, indicating increased brain functional activity. The CG showed essentially no voltage changes. The IG decreased times in the first trail making test from 94 to 57 seconds, and decreased time to complete the second trail making test from 113 to 93 seconds. Descriptive statistics revealed the measures for the IG had statistical significance (P<0.5) for the second trail making test and strong positive trends for all other parameters. Topographic brain maps from the test revealed a representative picture of the changes from taking the supplement. CONCLUSIONS: In this pilot study, consumption of a proprietary MCT combination produced marked enhancement in brain activity 90 minutes after ingestion with significant increases in relation to topographical brain maps. Further investigation is warranted to determine optimal ingestion conditions and time to effect for this and similar products across various populations. EEG measurements show promise as assessment biomarkers for the effects of nutritional supplements on brain function.

Auditory middle latency responses differ in right- and left-handed subjects: an evaluation through topographic brain mapping.

To investigate the association of handedness with auditory middle latency responses (AMLRs) using topographic brain mapping by comparing amplitudes and latencies in frontocentral and hemispheric regions of interest (ROIs). The study included 44 healthy subjects with normal hearing (22 left handed and 22 right handed). AMLRs were recorded from 29 scalp electrodes in response to binaural 4-kHz tone bursts. Frontocentral ROI comparisons revealed that Pa and Pb amplitudes were significantly larger in the left-handed than the right-handed group. Topographic brain maps showed different distributions in AMLR components between the two groups. In hemispheric comparisons, Pa amplitude differed significantly across groups. A left-hemisphere emphasis of Pa was found in the right-handed group but not in the left-handed group. This study provides evidence that handedness is associated with AMLR components in frontocentral and hemispheric ROI. Handedness should be considered an essential factor in the clinical or experimental use of AMLRs.

Topographic voltage and coherence mapping of brain potentials by means of the symbolic resonance analysis

We apply the recently developed symbolic resonance analysis to electroencephalographic measurements of event-related brain potentials (ERPs) in a language processing experiment by using a three-symbol static encoding with varying thresholds for analyzing the ERP epochs, followed by a spin-flip transformation as a nonlinear filter. We compute an estimator of the signal-to-noise ratio (SNR) for the symbolic dynamics measuring the coherence of threshold-crossing events. Hence, we utilize the inherent noise of the EEG for sweeping the underlying ERP components beyond the encoding thresholds. Plotting the SNR computed within the time window of a particular ERP component (the N400) against the encoding thresholds, we find different resonance curves for the experimental conditions. The maximal differences of the SNR lead to the estimation of optimal encoding thresholds. We show that topographic brain maps of the optimal threshold voltages and of their associated coherence differences are able to dissociate the underlying physiological processes, while corresponding maps gained from the customary voltage averaging technique are unable to do so.

ERP evidence of a dichotic left-ear deficit in some dyslexic children.

Children with and without behavioral dichotic left-ear deficits participated in an event-related potential study with quasidichotic presentations of familiar fairy tale segments. Electrical activity was recorded from the scalp while the children listened for semantically and/or syntactically anomalous words from either the right side or the left side while competing segments of the fairy tale were simultaneously presented from the opposite side. Latencies and amplitudes were averaged for each target condition within the group with dichotic left-ear deficits (LED) and the group with normal dichotic listening performance (WNL). Individual global field power waveforms and topographic brain maps were generated for the average response in each of the two listening conditions, target right and target left. Cross-correlations were performed on the grand averaged global field power waveforms to measure the degree of synchrony between target right and target left responses in both groups. Integration functions were performed to compare the accumulated sum of voltages during target (right and left) and control (right and left) conditions. WNL children produced typical ERP responses to the target words in both target right and target left conditions. Responses from LED children were at delayed latencies in the target left condition and were at reduced amplitudes in both target conditions. Topographic brain maps revealed more lateralized scalp distributions and greater activation of frontal regions in LED children in the target left condition. Cross-correlational and integration function results demonstrated interaural asymmetries in responses from the LED children. Overall results suggest that slowed neural conduction times, poor interhemispheric transfer of neural activity, and a failure to suppress competing information arriving at the right ear may be involved in poor left-sided processing in children with behavioral left-ear dichotic deficits.

The magnitude of the central response to esophageal electrical stimulation is intensity dependent

BACKGROUND & AIMS: Cerebral evoked potential (EP) responses to visceral stimulation represent a powerful method to assess visceral afferent pathways. The aim of this study was to establish basic stimulation parameters (dose-response relationship in EP amplitude and topographic brain organization) during electrical esophageal stimulation. METHODS: Electrical esophageal stimulation was performed in repeated series of 24 stimuli in 15 healthy subjects (25 years) by steps of 5 mA, ranging from 0.5 mA (sham) to 25 mA. EPs were obtained using scalp electrodes positioned according to the 10/20 International electroencephalographic system. Topographic EP maps were created using interpolation techniques. RESULTS: No cerebral responses were recorded with sham stimulation. A significant intensity-dependent increase of the major EP peaks (N1-P2) was observed between 5 and 25 mA (P < 0.05). A significant shortening of the mean peak latency of the first peak (N1) occurred with increasing stimulus intensity (P < 0.0001). Topographic brain maps localized the early EP peaks centrally, whereas later peaks were spread symmetrically over the centroparietal region. CONCLUSIONS: The clear dose-response relationship in the brain response with increasing stimulus intensities probably reflects increased recruitment of afferent fibers. Early peaks originate from deep central brain structures, whereas later peaks are localized exclusively in cortical regions. (Gastroenterology 1997 Apr;112(4):1137-46)

The Effect of Spikes and Spike-Free Epochs on Topographic Brain Maps

Maps of foci, when no discharges nor obvious slow activity were included in the map, usually (84%) showed changes within the focus itself and also in adjacent areas (58%) and often (47%) in the mirror region. An increase in activity was more often seen in the more active foci, especially in the delta and beta 2 ranges, and decrease in activity was usually seen with inactive foci. When discharges were included in the maps, an increasing number was associated with an increase at the main focus in all ranges, especially in delta and beta 1, but much less often in beta 2. The amount of electrical charge required for a change in the map with spikes was approximately 40 nanocoulombs (nC) for the first and second changes, increasing to around 50 nC with adjacent or separate foci. "Artificial" spikes produce more delta activity than other frequency ranges and the FFT of various pulses show maximal amplitudes at the slowest frequencies.

Topographic brain mapping of EEG after acute application of ergotalkaloids in the elderly

In a double-blind, placebo-controlled, crossover study the encephalotropic and nootropic effects of single doses of two ergotalkaloids (30 and 60 mg nicergoline and 5 mg co-dergocrine mesylate (CDM)) were investigated in 12 elderly subjects (mean age 67 years), utilizing topographic brain mapping of the EEG. Evaluation of EEG, memory, pulse and blood pressure were carried out at 0, 2, 4, 6 and 8 h. Topographic brain maps demonstrated an augmentation of total power, an acceleration of the centroid of the total activity, a decrease of delta/theta and an increase of beta activity (mostly in the alpha-adjacent frequency bands), as well as an acceleration of the centroid of the delta/theta and a slowing of the beta centroid. These changes are indicative of improvement in vigilance of elderly subjects after ergotalkaloids, which was also reflected in the significant improvement of memory after nicergoline. Topographically, the main effect was found over the frontal, central and temporal regions. Timewise, the pharmacodynamic peak fell into the 4th h, although with 60 mg significant encephalotropic effects could be observed in the 2nd and in the 6th h. The drugs were well tolerated.

CT-CBF correlations of cognitive deficits in multi-infarct dementia.

Fifteen right-handed patients with Multi-Infarct Dementia underwent cognitive testing by the Jacobs Mini-Mental Scale (MMQ), and xenon contrast CT scanning. Local cerebral blood flow (LCBF) and local partition coefficient (L lambda) values were measured by stable xenon contrast CT scanning and potential methodological errors were discussed. Reduced values were graded: 0 = normal, 1 = mild, 2 = moderate, 3 = severe. Graded values were pooled and plotted on composite brain maps to display locations of abnormal L lambda and LCBF values. Topographic brain maps, showing most frequent locations of reduced L lambda values, confirmed the common anatomical locations of multiple cerebral infarcts to be distributed in both thalami, temporal lobes, basal ganglia, left internal capsule and right cingulate cortex. Gray matter flow values were reduced in similar cortical and subcortical regions. There were no correlations between MMQ scores and reduced LCBF values for caudate and lenticular nuclei. Direct and statistically significant correlations were found between reduced MMQ scores and mean LCBF values for left or right frontal cortex, left or right temporal cortex and left or right thalamus. Subgrouping MMQ tests according to functions assessed, indicated that left mid-temporal ischemia correlated with dyscalculia and memory disturbances while ischemia of both frontal lobes correlated with disorientation to time and place.