Dr. Fahad Sultan
Organization: Hertie Institute for Clinical Brain Research
Phone number: +49 (0)7071 29 80464
Department: Dept. of Cognitive Neurology
Area: CIN Members
Field of Research
The unparalleled expansion of the human brain following an evolutionary process, accompanied by a number of adaptations that we share with our fellow primates, underlies many of our higher cognitive abilities. Understanding these adaptations and relating them to the human cognitive abilities that emerged is important for several diseases of the human brain (e.g., autism). In this lab we compare non-human primates with human gaze-following ability, and map the brain with functional magnetic resonance imaging (fMRI) to identify the relevant regions for social interaction. We also compare subcortical regions in the primate cerebellum and relate these to specializations in network architecture of the human brain. Together with Nikos K. Logothetis from the MPI for Biological Cybernetics we use electrical stimulation to study the output of these specialized networks with fMRI and show that these regions in the subcortex target widespread cortical networks.
Correlated Human and Monkey fMRI
Gaze direction may serve as a key to developing an understanding of another person’s interests and possible intentions. During very early development humans make use of eye-gaze, (the orientation of someone else’s eyes) and impaired processing of gaze information may be the basis of disturbances of social communication such as autism. We have used fMRI to delineate the relevant areas in the human brain and analogue areas in the monkey brain, which will be explored in the long run using electrophysiological techniques. Results show that the posterior part of the STS region und the cuneus are speciﬁcally involved in extracting and using detailed directional information from another person’s eyes to redirect one’s gaze and establish joint attention. In our study of the relative contributions of eye and head direction in gaze-following we asked whether a single brain region processes gaze in space, or whether different regions code eye-in-head and head-in-space separately. Our results support the hypothesis that the human equivalent of the gaze sensitive area in monkeys lies in more anterior parts of the STS than previously thought. The main aim of our project to study the fMRI of gaze following in monkeys was identifying areas in the monkey brain that are functionally equivalent to those of humans, to allow us to draw inferences about properties of the activated areas in the human brain. We showed that gaze following activates a region in and around the superior temporal sulcus, whose location seems to correspond to the area seen in the corresponding experiments on humans.
Unravelling a Cerebellar High-Frequency Pathway Targeting Extensive Motor, Sensory and Parietal Cortical Networks
Electrical stimulation of the gateway of the cerebellar output, the deep cerebellar nuclei (DCN), leads to reliable transsynaptic responses in the neocortex. Stimulation of the neocortex revealed the presence of strong inhibition, thus preventing the propagation of electrically-induced activation over multi-synaptic pathways. Stimulating the DCN we observed stimulation-induced BOLD activity in classical cerebellar receiving regions such as primary motor cortex, as well as in a number of additional areas in insular, parietal and occipital cortex, including all major sensory cortical representations. Our results also show that stimulating area V5/MT and surrounding areas leads to positive BOLD responses in the majority of cortical areas known to receive direct/monosynaptic connections from the stimulation site.
Comparative Anatomy of the Primate Dentate
The peculiar shape and large size of the human dentate nucleus, which is the largest single structure linking the cerebellum to the rest of the brain, have sparked a number of theories about the role of the cerebellum in human evolution. Comparative studies of humans and apes are hindered because of the complex three-dimensional shape of the human dentate. To facilitate correspondence with MRI-based material we built a 3D model based on a quantitative reconstruction of histological sections of the human dentate. Our model shows that the thicker ventral lamella occupies a distinctly smaller portion of the human dentate than previously hypothesized. The unique feature of the hominid dentate is the development of a large surface area and an expansion of its mediolateral width. We propose that this is to allow for a large number of independent corticonuclear modules that can modulate an equal large number of sequential motor acts.