scholarly journals Visual Mental Imagery Activates Topographically Organized Visual Cortex: PET Investigations

1993 ◽  
Vol 5 (3) ◽  
pp. 263-287 ◽  
Author(s):  
Stephen M. Kosslyn ◽  
Nathaniel M. Alpert ◽  
William L. Thompson ◽  
Vera Maljkovic ◽  
Steven B. Weise ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Mental Imagery ◽  
Anterior Part ◽  
Imagery Task ◽  
Area 17 ◽  
Mental Images ◽  
Imagery Condition ◽  
Posterior Portion ◽  
Large Size ◽  
Positron Emission

Cerebral blood flow was measured using positron emission tomography (PET) in three experiments while subjects performed mental imagery or analogous perceptual tasks. In Experiment 1, the subjects either visualized letters in grids and decided whether an X mark would have fallen on each letter if it were actually in the grid, or they saw letters in grids and decided whether an X mark fell on each letter. A region identified as part of area 17 by the Talairach and Tournoux (1988) atlas, in addition to other areas involved in vision, was activated more in the mental imagery task than in the perception task. In Experiment 2, the identical stimuli were presented in imagery and baseline conditions, but subjects were asked to form images only in the imagery condition; the portion of area 17 that was more active in the imagery condition of Experiment 1 was also more activated in imagery than in the baseline condition, as was part of area 18. Subjects also were tested with degraded perceptual stimuli, which caused visual cortex to be activated to the same degree in imagery and perception. In both Experiments 1 and 2, however, imagery selectively activated the extreme anterior part of what was identified as area 17, which is inconsistent with the relatively small size of the imaged stimuli. These results, then, suggest that imagery may have activated another region just anterior to area 17. In Experiment 3, subjects were instructed to close their eyes and evaluate visual mental images of upper case letters that were formed at a small size or large size. The small mental images engendered more activation in the posterior portion of visual cortex, and the large mental images engendered more activation in anterior portions of visual cortex. This finding is strong evidence that imagery activates topographically mapped cortex. The activated regions were also consistent with their being localized in area 17. Finally, additional results were consistent with the existence of two types of imagery, one that rests on allocating attention to form a pattern and one that rests on activating stored visual memories.

The Depictive Nature of Visual Mental Imagery

1998 ◽  
pp. 221-227
Author(s):  
Norman Yujen Teng
Keyword(s):  
Content Analysis ◽  
Visual Cortex ◽  
Mental Imagery ◽  
Mental Representations ◽  
Image Representation ◽  
The Other ◽  
Mental Images ◽  
Visual Mental Imagery ◽  
Topographic Representation ◽  
The Brain

Tye argues that visual mental images have their contents encoded in topographically organized regions of the visual cortex, which support depictive representations; therefore, visual mental images rely at least in part on depictive representations. This argument, I contend, does not support its conclusion. I propose that we divide the problem about the depictive nature of mental imagery into two parts: one concerns the format of image representation and the other the conditions by virtue of which a representation becomes a depictive representation. Regarding the first part of the question, I argue that there exists a topographic format in the brain but that does not imply that there exists a depictive format of image representation. My answer to the second part of the question is that one needs a content analysis of a certain sort of topographic representations in order to make sense of depictive mental representations, and a topographic representation becomes a depictive representation by virtue of its content rather than its form.

scholarly journals Cortical excitability controls the strength of mental imagery

2016 ◽  
Author(s):  
Rebecca Keogh ◽  
Johanna Bergmann ◽  
Joel Pearson
Keyword(s):  
Visual Cortex ◽  
Mental Imagery ◽  
Visual Imagery ◽  
Cortical Excitability ◽  
Mental Health Research ◽  
Causative Role ◽  
Mental Images ◽  
Neurophysiological Mechanism ◽  
Early Visual Cortex ◽  
Sensory Imagery

AbstractMental imagery provides an essential simulation tool for remembering the past and planning the future, with its strength affecting both cognition and mental health. Research suggests that neural activity spanning prefrontal, parietal, temporal, and visual areas supports the generation of mental images. Exactly how this network controls the strength of visual imagery remains unknown. Here, brain imaging and transcranial magnetic phosphene data show that lower resting activity and excitability levels in early visual cortex (V1-V3) predict stronger sensory imagery. Electrically decreasing visual cortex excitability using tDCS increases imagery strength, demonstrating a causative role of visual cortex excitability in controlling visual imagery. These data suggest a neurophysiological mechanism of cortical excitability involved in controlling the strength of mental images.

Impact of fMRI Acoustic Noise on the Functional Anatomy of Visual Mental Imagery

2002 ◽  
Vol 14 (2) ◽  
pp. 172-186 ◽  
Author(s):  
A. Mazard ◽  
B. Mazoyer ◽  
O. Etard ◽  
N. Tzourio-Mazoyer ◽  
S.M. Kosslyn ◽  
...  
Keyword(s):  
Blood Flow ◽  
Mental Imagery ◽  
Acoustic Noise ◽  
Anterior Cingulate ◽  
Imagery Task ◽  
Activation Pattern ◽  
Imagery Condition ◽  
Temporal Area ◽  
Visual Mental Imagery ◽  
Calcarine Cortex

One drawback of functional magnetic resonance imaging (fMRI) is that the subject must endure intense noise during testing. We examined the possible role of such noise on the activation of early visual cortex during visual mental imagery. We postulated that noise may require subjects to work harder to pay attention to the task, which in turn could alter the activation pattern found in a silent environment. To test this hypothesis, we used positron emission tomography (PET) to monitor regional Cerebral Blood Flow (rCBF) of six subjects while they performed an imagery task either in a silent environment or in an “fMRI-like” noisy environment. Both noisy and silent imagery conditions, as compared to their respective baselines, resulted in activation of a bilateral frontoparietal network (related to spatial processing), a bilateral inferior temporal area (related to shape processing), and deactivation of anterior calcarine cortex. Among the visual areas, rCBF increased in the most posterior part of the calcarine cortex, but at level just below the statistical threshold. However, blood flow values in the calcarine cortex during the silent imagery condition (but not the noisy imagery condition) were strongly negatively correlated with accuracy; the more challenging subjects found the task, the more strongly the calcarine cortex was activated. The subjects made more errors in the noisy condition than in the silent condition, and a direct comparison of the two conditions revealed that noise resulted in an increase in rCBF in the anterior cingulate cortex (involved in performance monitoring) and in the Wernicke's area (required to encode the verbal cues used in the task). These results thus demonstrate a nonadditive effect of fMRI gradient noise, resulting in a slight but significant effect on both performance and the neural activation pattern.

The projection from the lateral geniculate nucleus to the prestriate cortex of the macaque monkey

1981 ◽  
Vol 213 (1190) ◽  
pp. 73-80 ◽  
Keyword(s):  
Visual Cortex ◽  
Lateral Geniculate Nucleus ◽  
Macaque Monkey ◽  
Cell Distribution ◽  
Area 17 ◽  
Large Scatter ◽  
Large Size ◽  
Lateral Geniculate ◽  
Prestriate Cortex ◽  
The One

By injecting the enzyme horseradish peroxidase into the prestriate cortex of the macaque monkey and examining the lateral geniculate nucleus (l. g. n.) for retrograde label, the presence of a direct projection from the l. g. n. to prestriate visual cortex (Brodmann’s areas 18 and 19) was confirmed. Labelled cells occurred in all layers of the l. g. n., distributed in a roughly columnar fashion. The large scatter in cell distribution indicated a lower retinotopic precision for this projection than for the one to area 17. Labelled cells are of a medium to large size and, in each section, a few were located near the laminar border or in interlaminar zones. The functional significance of this projection is discussed.

scholarly journals Cortical excitability controls the strength of mental imagery

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Rebecca Keogh ◽  
Johanna Bergmann ◽  
Joel Pearson
Keyword(s):  
Visual Cortex ◽  
Mental Imagery ◽  
Visual Imagery ◽  
Cortical Excitability ◽  
Mental Health Research ◽  
Causative Role ◽  
Mental Images ◽  
Neurophysiological Mechanism ◽  
Early Visual Cortex ◽  
Sensory Imagery

Mental imagery provides an essential simulation tool for remembering the past and planning the future, with its strength affecting both cognition and mental health. Research suggests that neural activity spanning prefrontal, parietal, temporal, and visual areas supports the generation of mental images. Exactly how this network controls the strength of visual imagery remains unknown. Here, brain imaging and transcranial magnetic phosphene data show that lower resting activity and excitability levels in early visual cortex (V1-V3) predict stronger sensory imagery. Further, electrically decreasing visual cortex excitability using tDCS increases imagery strength, demonstrating a causative role of visual cortex excitability in controlling visual imagery. Together, these data suggest a neurophysiological mechanism of cortical excitability involved in controlling the strength of mental images.

scholarly journals Associative Imagery as a Strategy to Improve Destination Memory in Younger and Older Adults

2020 ◽  
Vol 4 (Supplement_1) ◽  
pp. 361-362
Author(s):  
Tara Johnson ◽  
Katie Stanko ◽  
Susan Jefferson
Keyword(s):  
Older Adults ◽  
Mental Imagery ◽  
Source Monitoring ◽  
Memory Performance ◽  
Grocery Store ◽  
Control Group ◽  
False Alarms ◽  
Imagery Condition ◽  
Destination Memory ◽  
Shared Information

Abstract Destination memory errors (inability to remember to whom information was shared) affects all ages, but older adults are particularly vulnerable due to poor source monitoring. Individuals may assume information was already shared when it was not or repeat previously shared information. The current study explored two mental imagery strategies (vivid imagery, visualizing context) to improve destination memory. Using a software program, younger and older adults told randomly generated facts to random celebrity faces. Participants were unaware of the upcoming memory tests. The control group did not use a strategy. The imagery group used vivid imagery to connect the fact and face (e.g., visualize Oprah on a dime to remember Oprah was told that dimes have 118 ridges). The context group visualized a provided context (e.g., grocery store) when telling a fact to a face. Assessments of performance on item memory (facts, faces) as well as destination memory (face-fact pairings) were counterbalanced. Results indicated an associative memory deficit among older adults, which was driven by a higher rate of false alarms. However, across all adults, the vivid imagery condition was more accurate than the control condition, and they demonstrated fewer false alarms. These findings suggest that older adults can use mental imagery to reduce false alarms and improve destination memory performance. Implications include reducing age stereotypes, improving conversations, and decreasing potentially dangerous situations (e.g., withholding important health information thinking it already was shared with a doctor).

Ferrier lecture - Functional architecture of macaque monkey visual cortex

1977 ◽  
Vol 198 (1130) ◽  
pp. 1-59 ◽  
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Receptive Field ◽  
Striate Cortex ◽  
Single Cells ◽  
Ocular Dominance ◽  
Receptive Fields ◽  
Macaque Monkey ◽  
Area 17 ◽  
Orientation Specificity

Of the many possible functions of the macaque monkey primary visual cortex (striate cortex, area 17) two are now fairly well understood. First, the incoming information from the lateral geniculate bodies is rearranged so that most cells in the striate cortex respond to specifically oriented line segments, and, second, information originating from the two eyes converges upon single cells. The rearrangement and convergence do not take place immediately, however: in layer IVc, where the bulk of the afferents terminate, virtually all cells have fields with circular symmetry and are strictly monocular, driven from the left eye or from the right, but not both; at subsequent stages, in layers above and below IVc, most cells show orientation specificity, and about half are binocular. In a binocular cell the receptive fields in the two eyes are on corresponding regions in the two retinas and are identical in structure, but one eye is usually more effective than the other in influencing the cell; all shades of ocular dominance are seen. These two functions are strongly reflected in the architecture of the cortex, in that cells with common physiological properties are grouped together in vertically organized systems of columns. In an ocular dominance column all cells respond preferentially to the same eye. By four independent anatomical methods it has been shown that these columns have the form of vertically disposed alternating left-eye and right-eye slabs, which in horizontal section form alternating stripes about 400 μm thick, with occasional bifurcations and blind endings. Cells of like orientation specificity are known from physiological recordings to be similarly grouped in much narrower vertical sheeet-like aggregations, stacked in orderly sequences so that on traversing the cortex tangentially one normally encounters a succession of small shifts in orientation, clockwise or counterclockwise; a 1 mm traverse is usually accompanied by one or several full rotations through 180°, broken at times by reversals in direction of rotation and occasionally by large abrupt shifts. A full complement of columns, of either type, left-plus-right eye or a complete 180° sequence, is termed a hypercolumn. Columns (and hence hypercolumns) have roughly the same width throughout the binocular part of the cortex. The two independent systems of hypercolumns are engrafted upon the well known topographic representation of the visual field. The receptive fields mapped in a vertical penetration through cortex show a scatter in position roughly equal to the average size of the fields themselves, and the area thus covered, the aggregate receptive field, increases with distance from the fovea. A parallel increase is seen in reciprocal magnification (the number of degrees of visual field corresponding to 1 mm of cortex). Over most or all of the striate cortex a movement of 1-2 mm, traversing several hypercolumns, is accompanied by a movement through the visual field about equal in size to the local aggregate receptive field. Thus any 1-2 mm block of cortex contains roughly the machinery needed to subserve an aggregate receptive field. In the cortex the fall-off in detail with which the visual field is analysed, as one moves out from the foveal area, is accompanied not by a reduction in thickness of layers, as is found in the retina, but by a reduction in the area of cortex (and hence the number of columnar units) devoted to a given amount of visual field: unlike the retina, the striate cortex is virtually uniform morphologically but varies in magnification. In most respects the above description fits the newborn monkey just as well as the adult, suggesting that area 17 is largely genetically programmed. The ocular dominance columns, however, are not fully developed at birth, since the geniculate terminals belonging to one eye occupy layer IVc throughout its length, segregating out into separate columns only after about the first 6 weeks, whether or not the animal has visual experience. If one eye is sutured closed during this early period the columns belonging to that eye become shrunken and their companions correspondingly expanded. This would seem to be at least in part the result of interference with normal maturation, though sprouting and retraction of axon terminals are not excluded.

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