INS NYC 2024 Program

Poster	Poster Session 04 Program Schedule 02/15/2024 12:00 pm - 01:15 pm Room: Majestic Complex (Posters 61-120) Poster Session 04: Neuroimaging \| Neurostimulation/Neuromodulation \| Teleneuropsychology/Technology Final Abstract #107 Perceptual Discrimination Following Lesions to Hippocampal vs. Thalamic Brain Regions Caitlin Terao, Department of Psychology, York University, Toronto, Canada Morgan Barense, Department of Psychology, University of Toronto, Toronto, Canada R. Shayna Rosenbaum, Department of Psychology, York University, Toronto, Canada Category: Memory Functions/Amnesia Keyword 1: thalamus Keyword 2: face processing Keyword 3: hippocampus Objective: The hippocampus, surrounding medial temporal lobe structures, and their major outputs play well-established roles in memory. More recent evidence, however, suggests that these regions may also differentially contribute to complex perceptual discrimination based on stimulus type and associated processing demands. In adult-onset amnesia, there are dissociable patterns of spared and impaired perceptual discrimination performance. Damage to the hippocampus, which provides direct input to the anterior nucleus of the thalamus via the fornix and mammillary bodies, is associated with reduced perceptual discrimination of spatial scenes, whereas damage to the perirhinal cortex, which provides direct input to the medial dorsal nucleus of the thalamus (MDN), is associated with reduced perceptual discrimination of objects and faces. It is unclear if compromise in early development to these structures or to their major outputs would result in similar patterns of impairment. The current study examined the performance of two individuals with developmental amnesia due to atypical development of the hippocampus, fornix, and mammillary bodies (case H.C.) vs. MDN (case N.C.) relative to controls on measures of complex perceptual discrimination. Participants and Methods: At the time of testing, H.C. was a 22-year-old female with agenesis of the mammillary bodies and anterior fornices and atypical prenatal development of the hippocampus, and N.C. was a 21-year-old male who experienced an early-onset stroke primarily affecting the right MDN. The control group consisted of age- and education-matched neurotypical individuals. Perceptual discrimination was measured using an oddity paradigm in which participants must identify the odd-one-out among four stimuli. Stimulus categories included size, colour, high-ambiguity artificial and everyday objects, and low- and high-ambiguity faces and scenes. Modified t-tests for comparing a single case to a small control group were used to compare H.C.’s and N.C.’s performance to that of controls. Results: H.C. and N.C. demonstrated intact perceptual discrimination of size, colour, high-ambiguity artificial and everyday objects, low-ambiguity faces, and low- and high-ambiguity scenes relative to controls (all t < 0.942; all p > .146). For the discrimination of high-ambiguity faces, H.C. showed similarly intact performance (t = -0.125, p = .452), whereas N.C. showed significant impairment relative to controls (t = 2.872, p = .012). Conclusions: H.C.’s performance was indistinguishable from that of controls, whereas N.C. demonstrated selective impairment for high-ambiguity faces. H.C.’s intact performance suggests that reorganization of function may have occurred in relation to the prenatal nature of her pathology. N.C.’s selective impairment provides evidence that as a major output of the perirhinal cortex, the MDN uniquely contributes to stimulus-specific perceptual discrimination. Namely, the MDN supports the complex perceptual discrimination of face stimuli. The results indicate dissociable patterns of spared and impaired perceptual discrimination following early-onset compromise to brain regions that were long viewed as playing a specialized role in memory.

Poster

02/15/2024
12:00 pm - 01:15 pm
Room: Majestic Complex (Posters 61-120)

Poster Session 04: Neuroimaging | Neurostimulation/Neuromodulation | Teleneuropsychology/Technology

Final Abstract #107

Perceptual Discrimination Following Lesions to Hippocampal vs. Thalamic Brain Regions

Caitlin Terao, Department of Psychology, York University, Toronto, Canada
Morgan Barense, Department of Psychology, University of Toronto, Toronto, Canada
R. Shayna Rosenbaum, Department of Psychology, York University, Toronto, Canada

Category: Memory Functions/Amnesia

Keyword 1: thalamus
Keyword 2: face processing
Keyword 3: hippocampus

Objective:

The hippocampus, surrounding medial temporal lobe structures, and their major outputs play well-established roles in memory. More recent evidence, however, suggests that these regions may also differentially contribute to complex perceptual discrimination based on stimulus type and associated processing demands. In adult-onset amnesia, there are dissociable patterns of spared and impaired perceptual discrimination performance. Damage to the hippocampus, which provides direct input to the anterior nucleus of the thalamus via the fornix and mammillary bodies, is associated with reduced perceptual discrimination of spatial scenes, whereas damage to the perirhinal cortex, which provides direct input to the medial dorsal nucleus of the thalamus (MDN), is associated with reduced perceptual discrimination of objects and faces. It is unclear if compromise in early development to these structures or to their major outputs would result in similar patterns of impairment. The current study examined the performance of two individuals with developmental amnesia due to atypical development of the hippocampus, fornix, and mammillary bodies (case H.C.) vs. MDN (case N.C.) relative to controls on measures of complex perceptual discrimination.

Participants and Methods:

At the time of testing, H.C. was a 22-year-old female with agenesis of the mammillary bodies and anterior fornices and atypical prenatal development of the hippocampus, and N.C. was a 21-year-old male who experienced an early-onset stroke primarily affecting the right MDN. The control group consisted of age- and education-matched neurotypical individuals. Perceptual discrimination was measured using an oddity paradigm in which participants must identify the odd-one-out among four stimuli. Stimulus categories included size, colour, high-ambiguity artificial and everyday objects, and low- and high-ambiguity faces and scenes. Modified t-tests for comparing a single case to a small control group were used to compare H.C.’s and N.C.’s performance to that of controls.

Results:

H.C. and N.C. demonstrated intact perceptual discrimination of size, colour, high-ambiguity artificial and everyday objects, low-ambiguity faces, and low- and high-ambiguity scenes relative to controls (all t < 0.942; all p > .146). For the discrimination of high-ambiguity faces, H.C. showed similarly intact performance (t = -0.125, p = .452), whereas N.C. showed significant impairment relative to controls (t = 2.872, p = .012).

Conclusions:

H.C.’s performance was indistinguishable from that of controls, whereas N.C. demonstrated selective impairment for high-ambiguity faces. H.C.’s intact performance suggests that reorganization of function may have occurred in relation to the prenatal nature of her pathology. N.C.’s selective impairment provides evidence that as a major output of the perirhinal cortex, the MDN uniquely contributes to stimulus-specific perceptual discrimination. Namely, the MDN supports the complex perceptual discrimination of face stimuli. The results indicate dissociable patterns of spared and impaired perceptual discrimination following early-onset compromise to brain regions that were long viewed as playing a specialized role in memory.