Visual angle of the mind's eye before and after unilateral occipital lobectomy.

Abstract

Do mental images occur in a spatially mapped (i.e., analog, or array-format) representational medium? Kosslyn's (1978) method was used to measure the visual angle of "the mind's eye" to estimate the extent of the imagery medium before and after unilateral occipital lobectomy. It was found that the overall size of the largest possible image was reduced following the surgery. In addition, only the horizontal extent, and not the vertical extent, of the imagery medium was reduced. Finally, it was determined that the S understood the tasks, was not aware of our predictions, and was unaffected by a strong demand characteristic in a different imagery task. These results are consistent with the hypothesis that imagery occurs in a spatially mapped representational medium dependent on occipital cortex.

Word meaning in the ventral visual path: a perceptual to conceptual gradient of semantic coding

“…These results suggest that early visual areas play a role in semantics, and not only in lowlevel vision, and they are coherent with recent studies indicating that activity in primary visual cortex contains perceptual information even in the absence of sensory stimulation (e.g., the prototypical color of objects presented as a gray-scale image) (Bannert and Bartels, 2013) or in presence of ambiguous stimuli (Vandenbroucke et al, 2014). Our results also relate to the literature on mental imagery, which indicates commonalities between the neural substrates of perception and of imagery (Farah, 1992;Kosslyn, 2001;Smith and Goodale, 2014). In our experiment we neither explicitly prompted the use of mental imagery nor did we inhibit it, thus we are neutral with respect to the issue of whether the observed effects were related to imagery or not.…”

Are Theories of Imagery Theories of Imagination? An Active Perception Approach to Conscious Mental Content

“…Although Kosslyn and others (Kosslyn et al, 1993;Damasio et al, 1993;Kosslyn, Thompson, Kim, & Alpert, 1995) have detected activity in the relevant brain areas during visual imagery, other researchers (Roland & Gulyás, 1994;Mellet et al, 1996) find no such activity, and argue that imagery is more consistently associated with activity in other, non-retinotopically organized regions. Neurological patients who have lost the retinotopically mapped regions in one cerebral hemisphere, leaving them blind in the corresponding half of their visual field, show certain impaired imagery abilities in the blinded hemifield (Butter, Kosslyn, Mijovic-Prelec, & Riffle, 1997;Farah, Soso, & Dasheif, 1992). However, other patients suffering from cortical blindness due to damage in these areas seem to have relatively normal imagery (Chatterjee & Southwood, 1995).…”

Individual Differences in Cerebral Blood Flow in Area 17 Predict the Time to Evaluate Visualized Letters

“…These areas preserve the (approximate) spatial structure of the retina, and hence depict information. Moreover, when these areas are damaged, visual imagery is impaired ( e g , see Farah, Soso, & Dasheiff, 1992). Recently, however, two laboratories have reported that they do not observe activation in the topographically organized areas of the occipital lobe during visual mental imagery (for a review, see Roland & Gulyas, 1994).…”