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Neuroscience

The Grand Challenge to Understand the Brain:

Neuroimaging by functional near-infrared spectroscopy

Joy Hirsch, PhD, Professor of Neurobiology and Psychiatry, Yale School of Medicine

Of all the challenges in the life sciences, understanding the brain is at the top of the list. The brain is the most complex organ of the body
with over 100,000,000,000 (billion) neurons along with other cells that make more than 100,000,000,000,000 (trillion) connections. These
connections are modulated by a multiplicity of neural chemical factors that span spatial scales starting with molecules, and progressing to
cells, circuits, systems, and finally leading to behavior including cognitive processes, emotions, perceptions, memories, and goal directed
actions. The worldwide prevalence of brain disorders at all stages of human development, from birth to end-of-life, constitutes significant
medical, political, economic, legal, and quality of life issues. Nonetheless, the brain, in health and disease, remains a scientific frontier.
The urgency of this widespread and unmet medical need alongside recent advances in neuroscience, however, has inspired the hopeful vision
that a comprehensive understanding of the brain is a realistic goal. This vision has recently been focused into an action plan in the United
States referred to as the BRAIN (Brain Research through Advancing Innovative Neurotechnologies) initiative. The initiative was launched on
April 2, 2013 by U.S. President Barack Obama who announced a Grand Challenge to “accelerate the development and application of new
technologies that will enable researchers to produce dynamic pictures of the brain that show how individual brain cells and complex neural
circuits interact at the speed of thought” (The White House, 2013). Subsequently, the National Institutes of Health (NIH) formulated a 10-year
plan to achieve the primary objective of accelerating the development of technology for acquiring fundamental insights about how the
nervous system functions in health and disease. A starting point for the BRAIN initiative is focused on the neural circuits in the brain including
characterization of the component cells, synaptic connections, and dynamic ensembles of activity associated with behavior. This overarching
objective spans multiple scales of investigation ranging from the molecular and cellular processes that govern short-range neural circuits to
long-range processes that govern complex behaviors observed by neuroimaging of humans.

Imaging the human brain in action information relevant to the processes of understanding language
and producing speech. Other brain areas that are widely recognized
A primary objective targeted for this initiative encompasses both the as essential for memory and emotion become functionally connected
improvement of existing technologies and the development of to the language system during specific tasks. The dynamic
entirely new technologies that interrogate and model relationships relationships among these interacting areas during language–related
between brain mechanisms and behaviors. Existing technologies for operations have been extensively studied using contemporary
brain mapping, predominantly using magnetic resonance imaging neuroimaging techniques.
(MRI) and electromagnetic techniques such as
magnetoencephalography (MEG) and electroencephalography (EEG),
are foundational for the investigation of the human brain under Technological advances
normal and pathological conditions. These technologies have
contributed extensively to a major branch of neuroscience focused Primarily due to the constraints of studying brain processes using
on the correlation of functional brain activity with cognition and magnetic resonance imaging (MRI) technologies, mainstream
behavior. In particular, the explosive growth in brain imaging neuroimaging has been limited to studies of single individuals.
technologies has led to an operational understanding of specialized Natural interpersonal interaction between two individuals is not
neural processes associated with complex cognitive behaviors such possible in a scanner environment. However, communication in real
as human language, memory, decision-making, vision and auditory time involves verbal and non-verbal exchanges including eye-to-eye
processes, emotions, learning and social interactions. contact, dynamic facial expressions, and responsive gestures. These
implicit communication cues do not occur in a scanning environment
including only one individual, although interactive social behavior
In general, the neural and physiological components that underlie
these systems are 1) localized to specific brain regions and involving dynamic communications between two individuals is a
short-range neural circuits that receive and transmit information, and fundamental aspect of human socialization. Largely due to these
2) are interconnected by long-range pathways between the technological limitations, little is known about the underlying neural
participating brain regions. Thus, two principles of brain organization circuits that regulate and modulate natural interpersonal interactions
emerge. The first is the principle of segregation where specific and communication. Consequently, the neurophysiological
regions of brain are dedicated to specific tasks and processing, and mechanisms of psychiatric conditions with potentially profound
the second is the principle of integration where co-active regions in deficits related to social interactions (e.g., autism spectrum disorders,
the brain are interconnected under specific task demands. For schizophrenia, anxiety, and depression) remain undefined. The
example, in the case of the human language system, a region development of new technologies for brain imaging during
located in the left superior temporal gyrus, often referred to as communication between two individuals in ecologically valid
Wernicke’s area, is specialized for receptive functions of language conditions presents a particularly impactful opportunity to address
(understanding and interpreting spoken words). Additionally, a the needs of large clinical populations for which the information
region located in the left inferior frontal gyrus, often referred to as gleaned through traditional neuroimaging is insufficient (Schilbach et
Broca’s Area, is specialized for productive language functions al., 2013).
(production of speech). These two complexes of specialized brain
regions are interconnected by well-known pathways, including the
arcuate fasciculus and the arcuate uncinate, that transmit

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