Objective:
The experiments covered by this protocol aim to uncover basic knowledge about the brain mechanisms that give rise to perception and cognition. The protocol encompasses sub-studies in volunteers ("participants") to uncover behaviors and their physiological basis. The protocol includes only non- or minimally invasive techniques with minimal risk, including psychophysics, functional magnetic resonance imaging (fMRI), magnetoencephalography (MEG), genetic sequencing, and on-line tests using web-based platforms. The overarching goal of the research is to obtain new knowledge in the organization and operation of cortical circuits involved in visual and auditory perception. The protocol covers six specific inter-related aims, with specific sub-studies:
1. Neurophysiological Mechanisms for Color
2. Object-Color Associations (Color Memory)
3. Connectivity of Functionally-Defined Regions
4. Homologies between Monkeys and Humans
5. Functional Organization of Sound Perception and Visual-Auditory Integration
6. Multi-stability in Color Perception
Study Population:
In-lab or on-line volunteer participants aged 18-65, who are in good general health and have normal or corrected-to-normal vision will be recruited from the local community and studied under this minimal risk protocol. We plan to recruit up to 100 in-person participants, 100 off-site participants, and up to 10,000 on-line volunteers. For off-site participants, the eligibility criteria will be ages 13-65. A subset of approximately 12 participants who are eligible and interested will be referred to this study (to the off-site cohort) from the Investigating Visual Recognition in Normal Populations and in Individuals with Recognition Impairment study at Dartmouth College (STUDY00022345).
Design:
In some sub-studies, the same subject will be asked to participate in tasks involving fMRI, MEG and psychophysics, and multiple sessions of each, so that we can control for individual differences in relating the outcomes of each experimental technique. In other sub-studies, participation in multiple tasks will not be required. The extent of the participant involvement, and what they will be asked to do, will be clearly disclosed during consent, as indicated in the consent documents. Brain activity will be monitored by fMRI and/or MEG. Anatomical magnetic resonance imaging (MRI) will be collected in some subjects to allow better localization of brain dynamics. Behavioral tests will be conducted using standard psychophysical approaches, involving presentation of visual and/or auditory stimuli while eye-movements are monitored using non-invasive eye tracking (such as with an infra-red camera directed at the participant's eyes). Subjects will be shown simple visual stimuli such as blobs, stripes, and spirals in assorted colors, moving dots, checkerboards, and every-day images and video clips, such as of fruit rolling on a tablecloth, faces, and scenery recorded in a car. Auditory stimuli will include every-day sounds such as birds singing, conversation, whispering, footsteps, car engines, and animal vocalizations, presented within normal sound limits (60- 90 dB). We will not use provocative or sexually explicit images, clips or sounds. During fMRI and MEG sessions, subjects will be asked to free view, passively fixate, or engage in an attentional task during fixation, such as reporting with an eye movement or button press occasions when two images of the same category are presented sequentially.
Outcome Measures:
Performance on behavioral tasks and brain activity (fMRI and MEG) will be combined to yield information about the neural correlates and processes underlying different aspects of the human neural visual processing stream including color perception, attention, visual discrimination and object/face/place recognition.
i. MRI: to analyze measures such as the anatomical structures of the brain (using structural MRI); amplitude of the blood-oxygenation-level-dependent (BOLD) signal \& using fMRI).
ii. MEG: to quantify measures such as power spectrum, event- or task-related potentials, synchronization/desynchronization, and coherence between sensors or sources located close to the brain areas of interest.
iii. Behavioral measures: to quantify measures such as hit rate, reaction times, thresholds, similarity judgments, associations, naming (such as names for color stimuli and sounds) and eye movements.
We may measure autonomic data during the course of the experiment (such as heart rate, respiration, end-tidal CO2, skin conductance), which will be correlated with the outcome measures.
