Transcript Exploring the neural basis of cognition: multi

September 2, 2009
Kamini Krishnan
Tandra Toon
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
Why Macaque Brains?
 Primates are closer to the human brain more than
any other species. Nature 453, 833 (2008)
 fMRI in Macaques have “potential to link finding
from human fMRI to those from macaque
neurophysiology.”
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
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
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)
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
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);
Intraparietal sulcus; Superior parietal lobule; Lateral bank of
Intraparietal sulcus
 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
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
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
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
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?