The etiology and experience-dependent modification of brain mapping signals

Perfusion-based neuroimaging techniques, such as functional magnetic resonance imaging (fMRI) and optical imaging of intrinsic signals (OIS), measure perfusion-related signals as a proxy for neuronal activity. In order to better understand these perfusion-related maps, it is essential to characterize the etiology of these signals and to determine what conditions alter neuro-vascular-metabolic relationships. This dissertation characterizes perfusion-related signals during periods of dynamic brain changes (i.e. development and experience-dependent plasticity) and characterizes the spatial and temporal relationship of different mapping modalities (OIS, fMRI, and electrocortical stimulation mapping [ESM]).; Characterization of optical responses during development and periods of experiential plasticity suggests that neuro-vascular-metabolic relationships may be modified during these periods. By simultaneously measuring electrophysiological and multiwavelength OIS responses throughout development in rodents, we show that while optical responses to whisker stimulation at some wavelengths (e.g. 850nm and 610nm phase II) change through the age of 12 weeks, optical responses at other wavelengths (e.g. 550nm and 610nm phase I) and electrophysiological responses appear relatively mature by 3 weeks of age. A possible dissociation of neurovascular coupling was also identified during experiential potentiation of optical responses. While electrophysiological and metabolic changes occur in rodents within days to one week following whisker plucking, potentiation of optical responses was not observed until after 2 weeks.; In order to better understand the etiology of BOLD fMRI signals, fMRI maps were compared with positive 610nm OIS and ESM. fMRI and OIS maps were highly spatially and temporally correlated, suggesting the two arise from a similar etiology (increased local blood flow and volume). fMRI and ESM also demonstrated good spatial agreement; the sensitivity of fMRI relative to ESM was near 100% while the specificity was ∼70%, suggesting that fMRI spatial extent is slightly broader than the area of cortical activity. The clinical utility of fMRI and OIS for preoperative planning are discussed in light of these findings. Finally, a case report demonstrates how OIS can be used in humans to map cognitive processes: we demonstrate that different languages within a bilingual's brain activate both overlapping and distinct cortical areas.