scholarly journals When brain damage “improves” perception: neglect patients can localize motion-shifted probes better than controls

2015 ◽  
Vol 114 (6) ◽  
pp. 3351-3358 ◽  
Author(s):  
Stefania de Vito ◽  
Marine Lunven ◽  
Clémence Bourlon ◽  
Christophe Duret ◽  
Patrick Cavanagh ◽  
...  
Keyword(s):  
Right Hemisphere ◽  
Visual Fields ◽  
Critical Factor ◽  
Significant Shift ◽  
Stimulus Motion ◽  
Attentional Processes ◽  
Position Shift ◽  
The Right ◽  
High Level ◽  
Better Than

When we look at bars flashed against a moving background, we see them displaced in the direction of the upcoming motion (flash-grab illusion). It is still debated whether these motion-induced position shifts are low-level, reflexive consequences of stimulus motion or high-level compensation engaged only when the stimulus is tracked with attention. To investigate whether attention is a causal factor for this striking illusory position shift, we evaluated the flash-grab illusion in six patients with damaged attentional networks in the right hemisphere and signs of left visual neglect and six age-matched controls. With stimuli in the top, right, and bottom visual fields, neglect patients experienced the same amount of illusion as controls. However, patients showed no significant shift when the test was presented in their left hemifield, despite having equally precise judgments. Thus, paradoxically, neglect patients perceived the position of the flash more veridically in their neglected hemifield. These results suggest that impaired attentional processes can reduce the interaction between a moving background and a superimposed stationary flash, and indicate that attention is a critical factor in generating the illusory motion-induced shifts of location.

scholarly journals Right Hemisphere Activation of Joke-related Information: An Event-related Brain Potential Study

2005 ◽  
Vol 17 (3) ◽  
pp. 494-506 ◽  
Author(s):  
Seana Coulson ◽  
Ying Choon Wu
Keyword(s):  
Priming Effect ◽  
Right Hemisphere ◽  
Visual Fields ◽  
Relevant Information ◽  
Task Demands ◽  
Hemispheric Differences ◽  
Brain Potentials ◽  
Related Information ◽  
The Right ◽  
High Level

Two studies tested the hypothesis that the right hemisphere engages in relatively coarse semantic coding that aids high-level language tasks such as joke comprehension. Scalp-recorded event-related brain potentials (ERPs) were collected as healthy adults read probe words (CRAZY) preceded either by jokes or nonfunny controls (“Everyone had so much fun jumping into the swimming pool, we decided to put in a littlewater/platform”). Probes were related to the meaning of the jokes, but not the controls. In Experiment 1a, with central presentation, probes following jokes (related) elicited less negative ERPs 300–700 msec postonset (N400) than did probes following nonfunny controls (unrelated). This finding suggests related probes were primed by the jokes. In addition, unrelated probes elicited a larger anterior positivity 700– 900 msec than did related, as irrelevant stimuli impacted control processes invoked by task demands. In Experiment 1b, probes (CRAZY) were preceded only by sentence-final words from jokes (water) or controls (platform). No ERP effects were observed in Experiment 1b, suggesting the N400 priming effect and the anterior positivity observed in Experiment 1a reflect semantic activations at the discourse level. To assess hemispheric differences in semantic activations, in Experiment 2, ERPs were recorded as participants read probe words presented in their left and right visual fields (LVF and RVF, respectively). Probes elicited a smaller N400 component when preceded by jokes than controls. This N400 priming effect was larger with presentation to the LVF, suggesting joke-relevant information was more active in the right hemisphere. The anterior positivity was observed with RVF but not LVF presentation, suggesting an important role for the left hemisphere in controlled retrieval in language comprehension.

scholarly journals Decreases in Frontal and Parietal Lobe Regional Cerebral Blood Flow Related to Habituation

1992 ◽  
Vol 12 (4) ◽  
pp. 546-553 ◽  
Author(s):  
Steven Warach ◽  
Ruben C. Gur ◽  
Raquel E. Gur ◽  
Brett E. Skolnick ◽  
Walter D. Obrist ◽  
...  
Keyword(s):  
Right Hemisphere ◽  
Parietal Lobe ◽  
Brain Activity ◽  
Inhalation Technique ◽  
Attentional Processes ◽  
Left Handed ◽  
Verbal Tasks ◽  
Spatial Tasks ◽  
Regional Specificity ◽  
The Right

We previously reported decreased mean CBF between consecutive resting conditions, ascribed to habituation. Here we address the regional specificity of habituation over three consecutive flow studies. Regional CBF (rCBF) was measured in 55 adults (12 right-handed men, 12 right-handed women, 14 left-handed men, 17 left-handed women), with the 133Xe inhalation technique, during three conditions: Resting, verbal tasks (analogies), and spatial tasks (line orientation). Changes in rCBF attributable to the cognitive tasks were eliminated by correcting these values to a resting equivalent. There was a progressive decrease in mean rCBF over time, reflecting habituation. This effect differed by region, with specificity at frontal (prefrontal, inferior frontal, midfrontal, superior frontal) and inferior parietal regions. In the inferior parietal region, habituation was more marked in the left than the right hemisphere. Right-handers showed greater habituation than did left-handers. There was no sex difference in global habituation, but males showed greater left whereas females showed greater right hemispheric habituation. The results suggest that habituation to the experimental setting has measurable effects on rCBF, which are differently lateralized for men and women. These effects are superimposed on task activation and are most pronounced in regions that have been implicated in attentional processes. Thus, regional decrement in brain activity related to habituation seems to complement attentional effects, suggesting a neural network for habituation reciprocating that for attention.

Vocal Reaction Times to Tachistoscopically Presented High- and Low-Frequency Verbs: Some Evidence for Selective Minor Hemisphere Linguistic Analysis

1988 ◽  
Vol 66 (3) ◽  
pp. 803-810 ◽  
Author(s):  
Michael P. Rastatter ◽  
Catherine Loren
Keyword(s):  
Visual Field ◽  
High Frequency ◽  
Right Hemisphere ◽  
Visual Fields ◽  
Reaction Times ◽  
Low Frequency ◽  
Normal Subjects ◽  
Right Visual Field ◽  
Intact Brain ◽  
The Right

The current study investigated the capacity of the right hemisphere to process verbs using a paradigm proven reliable for predicting differential, minor hemisphere lexical analysis in the normal, intact brain. Vocal reaction times of normal subjects were measured to unilaterally presented verbs of high and of low frequency. A significant interaction was noted between the stimulus items and visual fields. Post hoc tests showed that vocal reaction times to verbs of high frequency were significantly faster following right visual-field presentations (right hemisphere). No significant differences in vocal reaction time occurred between the two visual fields for the verbs of low frequency. Also, significant differences were observed between the two types of verbs following left visual-field presentation but not the right. These results were interpreted to suggest that right-hemispheric analysis was restricted to the verbs of high frequency in the presence of a dominant left hemisphere.

scholarly journals Asymmetry in the content of brain monoamines of BALB/c mice reared in social isolation conditions

2012 ◽  
Vol 10 (4) ◽  
pp. 42-48 ◽  
Author(s):  
Inessa Vladimirovna Karpova ◽  
Vladimir Vladimirovich Mikheyev ◽  
Yevgeniy Rudolfovich Bychkov ◽  
Andrey Andreyevich Lebedev ◽  
Petr Dmitriyevich Shabanov
Keyword(s):  
Social Isolation ◽  
Elevated Level ◽  
Right Hemisphere ◽  
Brain Structures ◽  
Brain Monoamines ◽  
Left Hippocampus ◽  
The Right ◽  
High Level ◽  
The Brain

The effects of long-term social isolation on the content and metabolism of dopamine and serotonin systems were studied in symmetrical brain structures of BALB/c male mice. With HPLC the contents of dopamine (DA), serotonin (5-HT) and their metabolites dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindolacetic acid (5-HIAA) were measured in the cortex, hippocampus and striatum of both the right and the left hemispheres of the brain in mice reared in groups and social isolation. The isolated mice were characterized by reduced level of DA in the left striatum and elevated level of 5-HIAA and ratio 5-HIAA/5-HT in the right striatum. In the hippocampus of isolated mice, the activation of both DA-ergic and 5-HT-ergic systems was observed, that is the high level of DA and DOPAC in the left hippocampus and the elevated level of 5-HT in both hemispheres and of 5-HIAA in the right hippocampus were registered. On the other hand, the reduction of both DA-ergic and 5-HT-ergic systems activity was shown to be in the right hemisphere. The decreased concentration of DOPAC and ratio DOPAC/DA in the right cortex were observed as well. As to 5-HT-ergic system, the reduced level of 5-HT in the both cortex of the hemispheres as well as 5-HIAA in the right hemisphere of isolated mice was determined. The phenomenon of interhemispheric asymmetry was revealed in the hippocampus only, which was characterized by the increased DA-ergic activity in the left hippocampus but not in the striatum and the cortex.

scholarly journals Unified Visual Working Memory without the Anterior Corpus Callosum

Symmetry ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2106
Author(s):  
Yair Pinto ◽  
Edward H.F. de Haan ◽  
Maria-Chiara Villa ◽  
Sabrina Siliquini ◽  
Gabriele Polonara ◽  
...  
Keyword(s):  
Working Memory ◽  
Corpus Callosum ◽  
Visual Working Memory ◽  
Visual Information ◽  
Right Hemisphere ◽  
Visual Fields ◽  
Healthy Human ◽  
Visual Hemifield ◽  
The Right ◽  
Visual Hemifields

One of the most fundamental, and most studied, human cognitive functions is working memory. Yet, it is currently unknown how working memory is unified. In other words, why does a healthy human brain have one integrated capacity of working memory, rather than one capacity per visual hemifield, for instance. Thus, healthy subjects can memorize roughly as many items, regardless of whether all items are presented in one hemifield, rather than throughout two visual hemifields. In this current research, we investigated two patients in whom either most, or the entire, corpus callosum has been cut to alleviate otherwise untreatable epilepsy. Crucially, in both patients the anterior parts connecting the frontal and most of the parietal cortices, are entirely removed. This is essential, since it is often posited that working memory resides in these areas of the cortex. We found that despite the lack of direct connections between the frontal cortices in these patients, working memory capacity is similar regardless of whether stimuli are all presented in one visual hemifield or across two visual hemifields. This indicates that in the absence of the anterior parts of the corpus callosum working memory remains unified. Moreover, it is important to note that memory performance was not similar across visual fields. In fact, capacity was higher when items appeared in the left visual hemifield than when they appeared in the right visual hemifield. Visual information in the left hemifield is processed by the right hemisphere and vice versa. Therefore, this indicates that visual working memory is not symmetric, with the right hemisphere having a superior visual working memory. Nonetheless, a (subcortical) bottleneck apparently causes visual working memory to be integrated, such that capacity does not increase when items are presented in two, rather than one, visual hemifield.

Vocal Reaction Times of Stuttering Subjects to Tachistoscopically Presented Concrete and Abstract Words

1987 ◽  
Vol 30 (3) ◽  
pp. 306-310 ◽  
Author(s):  
Michael P. Rastatter ◽  
Carl Dell
Keyword(s):  
Language Processing ◽  
Right Hemisphere ◽  
Visual Fields ◽  
Reaction Times ◽  
Normal Subjects ◽  
Decision Task ◽  
Functional Localization ◽  
Past Data ◽  
Abstract Words ◽  
The Right

The present study was an attempt to investigate further the issues pertaining to cerebral organization for visual language processing in the stuttering population. Employing a lexical decision task, vocal reaction times were obtained for a group of 14 stutterers to unilateral, tachistoscopically presented concrete and abstract words. Results of an analysis of variance showed that a significant interaction occurred between visual fields and stimuli. Posthoc tests showed that the right hemisphere was superior for analyzing the concrete words while the left hemisphere was responsible for processing the abstract items. Compared to past data from normal subjects, these findings were interpreted as suggesting that some form of linguistic competition may exist between the two hemispheres, possibly reflecting a disturbance in functional localization in the stuttering population.

Right Hemisphere Memory Bias Does Not Extend to Involuntary Memories for Negative Scenes

Perception ◽  
2021 ◽  
Vol 50 (1) ◽  
pp. 27-38
Author(s):  
Ella K. Moeck ◽  
Nicole A. Thomas ◽  
Melanie K. T. Takarangi
Keyword(s):  
Visual Field ◽  
Left Hemisphere ◽  
Right Hemisphere ◽  
Visual Fields ◽  
Memory Bias ◽  
Right Visual Field ◽  
Hemispheric Differences ◽  
Involuntary Memory ◽  
Involuntary Memories ◽  
The Right

Attention is unequally distributed across the visual field. Due to greater right than left hemisphere activation for visuospatial attention, people attend slightly more to the left than the right side. As a result, people voluntarily remember visual stimuli better when it first appears in the left than the right visual field. But does this effect—termed a right hemisphere memory bias—also enhance involuntary memory? We manipulated the presentation location of 100 highly negative images (chosen to increase the likelihood that participants would experience any involuntary memories) in three conditions: predominantly leftward (right hemisphere bias), predominantly rightward (left hemisphere bias), or equally in both visual fields (bilateral). We measured subsequent involuntary memories immediately and for 3 days after encoding. Contrary to predictions, biased hemispheric processing did not affect short- or long-term involuntary memory frequency or duration. Future research should measure hemispheric differences at retrieval, rather than just encoding.

Wada Testing Reveals Frontal Lateralization for the Memorization of Words and Faces

2002 ◽  
Vol 14 (1) ◽  
pp. 116-125 ◽  
Author(s):  
W. M. Kelley ◽  
J. G. Ojemann ◽  
R. D. Wetzel ◽  
C. P. Derdeyn ◽  
C. J. Moran ◽  
...  
Keyword(s):  
Right Hemisphere ◽  
Temporal Cortex ◽  
Memory Formation ◽  
Wada Test ◽  
Memory Impairments ◽  
Reversible Lesion ◽  
The Right ◽  
Open Question ◽  
Normal Performance ◽  
Better Than

Neuroimaging studies have suggested that specific regions of the frontal and medial temporal cortex are engaged during memory formation. Further, there is specialization across these regions such that verbal materials appear to preferentially engage the left regions while nonverbal materials primarily engage the right regions. An open question, however, has been to what extent frontal regions contribute to successful memory formation. The present study investigates this question using a reversible lesion technique known as the Wada test. Patients memorized words and unfamiliar faces while portions of their left and right hemispheres were temporarily anesthetized with sodium amytal. Subsequent memory tests revealed that faces were remembered better than words following left-hemisphere anesthesia, whereas words were remembered better than faces following right-hemisphere anesthesia. Importantly, inspection of the circulation affected by the amytal further suggests that these memory impairments did not result from direct anesthetization of the medial temporal regions. Taken in the context of the imaging findings, these results suggest that frontal regions may also contribute to memory formation in normal performance.

scholarly journals Exploration of the Hemispheric Differences in Number Processing of the Brain

2012 ◽  
Vol 1 (2) ◽  
pp. 55-61
Author(s):  
Aaron Wyland Walters
Keyword(s):  
Reaction Time ◽  
Visual Field ◽  
Right Hemisphere ◽  
Visual Fields ◽  
Reaction Time Data ◽  
Right Visual Field ◽  
Hemispheric Differences ◽  
Time Data ◽  
Central Target ◽  
The Right

Abstract The current study explored how reaction time and accuracy differed in the left and right visual fields by altering various dot clusters in both number and organization. Researchers have hypothesized that the left hemisphere uses counting to judge small, disorganized clusters of objects accurately and that the right hemisphere uses estimation to judge clusters organized in geometric shape accurately. The current study tested both visual fields of participant’s with organized and unorganized clusters of dots. Dots were clustered between 3 and 12. The clusters were presented on separate sides of a computer screen to analyze visual field differences in counting and estimation. A central target was presented on the screen to maintain central focus for the visual fields. Data from 40 participants (30 men, 10 women) from a small liberal arts college indicated that when clusters reached between 7 and 8 dots, organization in the right visual field created inaccuracy in judgment. Reaction time data indicated that as number level increased, reaction time slowed. Reaction time data also showed that organization slowed reaction times in both visual fields. These data indicated that different numerical judgment abilities do exist within the hemispheres.

scholarly journals Fronto-parietal Organization for Response Times in Inhibition of Return: The FORTIOR Model

2017 ◽  
Author(s):  
Tal Seidel Malkinson ◽  
Paolo Bartolomeo
Keyword(s):  
Left Hemisphere ◽  
Inhibition Of Return ◽  
Right Hemisphere ◽  
Functional Organization ◽  
Response Times ◽  
Visual Fields ◽  
Response Threshold ◽  
Manual Response ◽  
Temporoparietal Junction ◽  
The Right

Inhibition of Return (IOR) refers to a slowing of response times (RTs) for visual stimuli repeated at the same spatial location, as compared to stimuli occurring at novel locations. The functional mechanisms and the neural bases of this phenomenon remain debated. Here we present FORTIOR, a model of the cortical control of visual IOR in the human brain. The model is based on known facts about the anatomical and functional organization of fronto-parietal attention networks, and accounts for a broad range of behavioral findings in healthy participants and brain-damaged patients. FORTIOR does that by combining four principles of asymmetry: a) Asymmetry in the networks topography, whereby the temporoparietal junction (TPJ) and ventrolateral prefrontal cortex (vlPFC) nodes are lateralized to the right hemisphere, causing higher activation levels in the right intraparietal sulcus (IPS) and frontal eye field (FEF) nodes. b) Asymmetry in inter-hemispheric connectivity, in which inter-hemispheric connections from left hemisphere IPS to right hemisphere IPS and from left hemisphere FEF to right hemisphere FEF are weaker than in the opposite direction. c) Asymmetry of visual inputs, stipulating that the FEF receives direct visual input coming from the ipsilateral visual cortex, while the right TPJ and vlPFC and IPS nodes receive input from both the contralateral and the ipsilateral visual fields. d) Asymmetry in the response modality, with a higher response threshold for the manual response system than that required to trigger a saccadic response. This asymmetry results in saccadic IOR being more robust to interference than manual IOR. FORTIOR accounts for spatial asymmetries in the occurrence of IOR after brain damage and after non-invasive transcranial magnetic stimulation on parietal and frontal regions. It also provides a framework to understand dissociations between manual and saccadic IOR, and makes testable predictions for future experiments to assess its validity.

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