September 2, 2009 Kamini Krishnan Tandra Toon

1. Exploring the neural basis of cognition: multi-modal links between human fMRI and macaque neurophysiology September 2, 2009 Kamini Krishnan Tandra Toon

2. Article Focus • Review of literature that combines use of functional or structural MRI and microelectrode techniques to macaque brains – allowing studies in macaque and humans to be linked. • Purpose: Investigate neurophysiological connections involved in human cognitive function

3. Why Macaque Brains? • Primates are closer to the human brain more than any other species. Nature453, 833 (2008) • fMRI in Macaques have “potential to link finding from human fMRI to those from macaque neurophysiology.”

4. Functional MRI • Uses blood oxygenation level-dependent (BOLD) signals • Records brain activity in real time during tasks • Explores internal states and high level cognitive functions

5. Additional Techniques Used • Microelectrode techniques • Alone and combined with fMRI • Structural MRI • Sucal landmark Comparisons • Cytoarchitectonics • Neurophysiological and Microstimulation • Diffusion Tensor MRI (DT-MRI) • Caveat: Homologous regions are not necessarily functionally equivalent

6. Using fMRI in humans and Macaques – Comparative Studies • Visual System • Functional comparative tasks (e.g., passive viewing, 3D perception, Face perception, saccadic eye movements, shape processing) • Similarities in visual areas are in “early visual areas” not necessarily in “higher visual areas” • Higher Level Cognitive Functions • Functional comparative tasks (e.g., cognitive set-shifting/cognitive flexibility)

7. fMRI comparison of Prefrontal Cortex Function • PFC - Involved in executive functions (e.g., working memory, planning, response inhibition) • Set-Shifting activation (cognitive flexibility) Areas of similarity from fMRI studies: caudal part of the inferior PFC • Mirror neurons (neuronal activation during observation of an action performed by others) Areas of similarity include Brodmann’s Area 44 and 45 – implication for the theory of the evolution of language

8. fMRI comparison of Oculomotor-Control Networks • Saccadic Eye Movements – neuronal network • Variances noted between macaques and humans • Areas of question include: Frontal Eye Field (BA 8 vs. BA 6); Intraparietalsulcus; Superior parietal lobule; Lateral bank of Intraparietalsulcus • Need to further improve task designs • 3D Perception • Inter-species differences in functional architecture of the IPS • Humans have four motion-sensitive regions; Macaques have one motion-sensitive area • Conclusion: Human IPS contains areas for visuospatial processing – Macaques do not

9. Combination of MRI and microelectrode techniques • Examines relationship between BOLD and neural signals • Detect local and global brain activation patterns induced by microstimulation (e.g., for visual areas) • Implications – Identify responsive brain regions to make appropriate decision for electrode-penetration sites

10. fMRI and combined Electrophysiology techniques • Somatosensory system • Primary and Secondary somatosensory cortices • High-level vision in face perception • Superior temporal sulcus • Localizing Cortical Recording Sites • Done during or just after a recording session; compliments existing localization methods that require post-mortem histology

11. Conclusion • fMRI and MRI-based techniques – bridge gap between human imaging studies and macaque neurophysiological studies • Direct comparison of functional brain structures • Multi-dimensional analyses of functional connectivity • Determines cortical recording sites

12. Questions and Discussion • What high-level cognitive functions could be explored? What would be limited? • What bias does the author have in publishing this article? • What are the implications of these studies to further understand human evolution?