Kevin C. Chan1,2, Matthew M. Cheung1,2,
Ed X. Wu1,2
1Laboratory of Biomedical Imaging and
Signal Processing, The University of Hong Kong, Hong Kong SAR, China; 2Department
of Electrical and Electronic Engineering, The University of Hong Kong, Hong
Kong SAR, China
In
the mammalian midbrain, increasing evidence suggested a direct projection
from the superior colliculus (SC) to the substantia nigra (SN), yet their
functional characteristics remain largely unknown. This study explores the
capability of blood oxygenation leveldependent (BOLD) fMRI to detect simultaneous
activations in SC and SN upon visual flash illumination in order to
understand the basic visual properties and hemodynamic responses in this
functional connection. Upon monocular stimulation, activations were found
predominantly in the contralateral SC and SN, whereas upon binocular
stimulation activations were observed in SC and SN of both hemispheres.
Significantly lower BOLD percent changes were also observed in the SN of both
groups than SC before reaching similar peak heights after stimulation. The
current results of having the same visual event initiating afferent inputs to
both SC and SN could have important implications for interpreting the
responses to biologically salient sensory events in relation to novelty,
intensity or reward within the SC-SN connection.