Visual mental imagery induces retinotopically organized activation of early visual areas.
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There is a long-standing debate as to whether visual mental imagery relies entirely on symbolic (language-like) representations or also relies on depictive (picture-like) representations. We sought to discover whether visual mental imagery could evoke cortical activity with precise visual field topography (retinotopy). Participants received three conditions: the perception condition consisted of a standard retinotopic mapping procedure, where two flickering checkerboard wedges rotated around a central fixation point. The imagery and attention conditions consisted of the same stimulus, but only the outer arcs of the wedges were visible. During imagery, participants mentally reproduced the stimulus wedges, using the stimulus arcs as a guide. The attention condition required either distributed attention or focused attention to where the stimulus wedges would have been. Event-related analysis revealed that the imagery (greater than either form of attention) retinotopic maps were similar to the perception maps. Moreover, blocked analysis revealed similar perception and imagery effects in human motion processing region MT+. These results support the depictive view of visual mental imagery. (+info)
A theory of mind investigation into the appreciation of visual jokes in schizophrenia.
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BACKGROUND: There is evidence that groups of people with schizophrenia have deficits in Theory of Mind (ToM) capabilities. Previous studies have found these to be linked to psychotic symptoms (or psychotic symptom severity) particularly the presence of delusions and hallucinations. METHODS: A visual joke ToM paradigm was employed where subjects were asked to describe two types of cartoon images, those of a purely Physical nature and those requiring inferences of mental states for interpretation, and to grade them for humour and difficulty. Twenty individuals with a DSM-lV diagnosis of schizophrenia and 20 healthy matched controls were studied. Severity of current psychopathology was measured using the Krawiecka standardized scale of psychotic symptoms. IQ was estimated using the Ammons and Ammons quick test. RESULTS: Individuals with schizophrenia performed significantly worse than controls in both conditions, this difference being most marked in the ToM condition. No relationship was found for poor ToM performance and psychotic positive symptomatology, specifically delusions and hallucinations. CONCLUSION: There was evidence for a compromised ToM capability in the schizophrenia group on this visual joke task. In this instance this could not be linked to particular symptomatology. (+info)
The dynamics of interhemispheric compensatory processes in mental imagery.
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The capacity to generate and analyze mental visual images is essential for many cognitive abilities. We combined triple-pulse transcranial magnetic stimulation (tpTMS) and repetitive TMS (rTMS) to determine which distinct aspect of mental imagery is carried out by the left and right parietal lobe and to reveal interhemispheric compensatory interactions. The left parietal lobe was predominant in generating mental images, whereas the right parietal lobe was specialized in the spatial comparison of the imagined content. Furthermore, in case of an rTMS-induced left parietal lesion, the right parietal cortex could immediately compensate such a left parietal disruption by taking over the specific function of the left hemisphere. (+info)
Imagery-induced cortical excitability changes in stroke: a transcranial magnetic stimulation study.
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Focal transcranial magnetic stimulation (TMS) was employed in a population of hemiparetic stroke patients in a post-acute stage to map out the abductor digiti minimi (ADM) muscle cortical representation of the affected (AH) and unaffected (UH) hemisphere at rest, during motor imagery and during voluntary contraction. Imagery induced an enhancement of the ADM map area and volume in both hemispheres in a way which partly corrected the abnormal asymmetry between AH and UH motor output seen in rest condition. The voluntary contraction was the task provoking maximal facilitation in the UH, whereas a similar degree of facilitation was obtained during voluntary contraction and motor imagery in the AH. We argued that motor imagery could induce a pronounced motor output enhancement in the hemisphere affected by stroke. Further, we demonstrated that imagery-induced excitability changes were specific for the muscle 'prime mover' for the imagined movement, while no differences were observed with respect to the stroke lesion locations. Present findings demonstrated that motor imagery significantly enhanced the cortical excitability of the hemisphere affected by stroke in a post-acute stage. Further studies are needed to correlate these cortical excitability changes with short-term plasticity therefore prompting motor imagery as a 'cortical reservoir' in post-stroke motor rehabilitation. (+info)
Enhanced vividness of mental imagery as a trait marker of schizophrenia?
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We assessed the vividness of mental imagery in schizophrenia patients in the context of psychopathology and cognitive abilities. A questionnaire on the vividness of mental imagery (Questionnaire Upon Mental Imagery [QMI]) and a hallucination scale were administered to 50 patients with paranoid schizophrenia. The related perceptual and cognitive skills, general intelligence level, and psychomotor speed were measured as covariates with a battery of performance tests. All measures were statistically compared to a group of 50 age- and sex-matched healthy controls. The schizophrenia group obtained higher values both for vividness of imagery and occurrence of hallucinations. These differences were independent of general intelligence and psychomotor speed and did not correlate with individual psychopathology. The correlation between the hallucination and imagery scales themselves was very low. These results suggest that patients with schizophrenia experience a significantly greater vividness of mental imagery than healthy controls, which does not seem to be an effect of other group differences or individual psychopathology (e.g., frequency of hallucinations). Vividness of mental imagery might thus prove to be an independent trait marker of schizophrenia. (+info)
Visual mental imagery during caloric vestibular stimulation.
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We investigated high-resolution mental imagery and mental rotation, while the participants received caloric vestibular stimulation. High-resolution visual mental imagery tasks have been shown to activate early visual cortex, which is deactivated by vestibular input. Thus, we predicted that vestibular stimulation would disrupt high-resolution mental imagery; this prediction was confirmed. In addition, mental rotation tasks have been shown to activate posterior parietal cortex, which is also engaged in the processing of vestibular stimulation. As predicted, we also found that mental rotation is impaired during vestibular stimulation. In contrast, such stimulation did not affect performance of a low-imagery control task. These data document previously unsuspected interactions between the vestibular system and the high-level visual system. (+info)
Mental concerts: musical imagery and auditory cortex.
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Most people intuitively understand what it means to "hear a tune in your head." Converging evidence now indicates that auditory cortical areas can be recruited even in the absence of sound and that this corresponds to the phenomenological experience of imagining music. We discuss these findings as well as some methodological challenges. We also consider the role of core versus belt areas in musical imagery, the relation between auditory and motor systems during imagery of music performance, and practical implications of this research. (+info)
Language and imagery: effects of language modality.
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Across spoken languages, properties of wordforms (e.g. the sounds in the word hammer) do not generally evoke mental images associated to meanings. However, across signed languages, many signforms readily evoke mental images (e.g. the sign HAMMER resembles the motion involved in hammering). Here we assess the relationship between language and imagery, comparing the performance of English speakers and British sign language (BSL) signers in meaning similarity judgement tasks. In experiment 1, we found that BSL signers used these imagistic properties in making meaning similarity judgements, in contrast with English speakers. In experiment 2, we found that English speakers behaved more like BSL signers when asked to develop mental images for the words before performing the same task. These findings show that language differences can bias users to attend more to those aspects of the world encoded in their language than to those that are not; and that language modality (spoken versus signed) can affect the degree to which imagery is involved in language. (+info)