Differentiation of Types of Visual Agnosia Using EEG

Abstract

Visual recognition deficits are the hallmark symptom of visual agnosia, a neuropsychological disorder typically associated with damage to the visual system. Most research into visual agnosia focuses on characterizing the deficits through detailed behavioral testing, and structural and functional brain scans are used to determine the spatial extent of any cortical damage. Although the hierarchical nature of the visual system leads to clear predictions about the temporal dynamics of cortical deficits, there has been little research on the use of neuroimaging methods with high temporal resolution to characterize the temporal profile of agnosia deficits. Here, we employed high-density electroencephalography (EEG) to investigate alterations in the temporal dynamics of the visual system in two individuals with visual agnosia. In the context of a steady state visual evoked potential paradigm (SSVEP), individuals viewed pattern-reversing checkerboards of differing spatial frequency, and we assessed the responses of the visual system in the frequency and temporal domain. JW, a patient with early visual cortex damage, showed impaired SSVEP response relative to a control group and to the second patient (SM) who had right temporal lobe damage. JW also showed lower decoding accuracy for early visual responses (around 100 ms). SM, whose lesion is more anterior in the visual system, showed good decoding accuracy initially but low decoding after 500 ms. Overall, EEG and multivariate decoding methods can yield important insights into the temporal dynamics of visual responses in individuals with visual agnosia.

Aging Enhances Neural Activity in Auditory, Visual, and Somatosensory Cortices: The Common Cause Revisited

“…Our findings are also consistent with studies showing that stroke-related prefrontal injury is often associated with increased amplitude and longer latencies for AEPs (Woods and Clayworth, 1986;Knight et al, 1989) and SEPs (Yamaguchi and Knight, 1990). This is in stark contrast with injury localized to temporal, parietal, or occipital regions, which are usually associated with decreased sensory-evoked response amplitude (Knight et al, 1980;Kileny et al, 1987;Woods et al, 1987;Alain et al, 1998;Haigh et al, 2018;Mammadkhanli et al, 2020).…”

Visual Representations: Insights from Neural Decoding

“…At the same time, neural decoding also lends itself well to single-participant analyses and can therefore provide insights into how visual representations are altered in cases of visual deficits (i.e., case studies). Various work has found neural correlates of representational differences in disorders such as prosopagnosia, a deficit in face recognition (Rivolta et al 2014), and visual object agnosia, a deficit in object recognition (Haigh et al 2018). There is almost endless possibility in this space, and future work will likely tackle in greater detail how representations vary during development, after brain injury, during healthy aging, and in clinical populations, among other circumstances.…”