The majority of functional neuroscience studies have focused on the brain's response to a task or stimulus. However, the brain is very active even in the absence of explicit input or output. In this Article we review recent studies examining spontaneous fluctuations in the blood oxygen level dependent (BOLD) signal of functional magnetic resonance imaging as a potentially important and revealing manifestation of spontaneous neuronal activity. Although several challenges remain, these studies have provided insight into the intrinsic functional architecture of the brain, variability in behaviour and potential physiological correlates of neurological and psychiatric disease.

/pdf/spontaneous-fluctuations-in-brain-activity-observed-with-32z1nyfc7n.pdf

Spontaneous fluctuations in brain activity observed with functional magnetic resonance imaging.

The synchronization of chaotic systems

Infants learn language with remarkable speed, but how they do it remains a mystery. New data show that infants use computational strategies to detect the statistical and prosodic patterns in language input, and that this leads to the discovery of phonemes and words. Social interaction with another human being affects speech learning in a way that resembles communicative learning in songbirds. The brain's commitment to the statistical and prosodic patterns that are experienced early in life might help to explain the long-standing puzzle of why infants are better language learners than adults. Successful learning by infants, as well as constraints on that learning, are changing theories of language acquisition.

/pdf/early-language-acquisition-cracking-the-speech-code-bf9adht4u8.pdf

Early language acquisition: cracking the speech code

http://www.iss.com/resources/pdf/publications/fnirs-history.pdf

A brief review on the history of human functional near-infrared spectroscopy (fNIRS) development and fields of application.

https://www.cell.com/trends/neurosciences/pdf/S0166-2236(97)01132-6.pdf

Non-invasive optical spectroscopy and imaging of human brain function

The effect of motor activity on the left fronto‐central region of the human brain was analyzedspatially and temporally by using noninvasive near‐infrared light (NIR) topography. The changes in oxygenation states caused by motor activity were measured using intensity‐modulated NIR spectroscopy at ten measurement positions on the head surface. The subject randomly performed unilateral finger opposition for 30 s as motor stimulation. When the subject performed contralateral (right) finger movement, significant increases in both oxygenated hemoglobin (oxy‐Hb) and total hemoglobin (total‐Hb) and decreases in deoxygenated hemoglobin (deoxy‐Hb) were observed in a particular area. By mapping the static topograms of the changes of each Hb and comparing them with an anatomical image of MRI, it was found that the particular area was located on the motor cortex along the central sulcus. By mapping the dynamic topograms of the changes of total‐Hb, which reflect the cerebral blood volume, and analyzing the spatiotemporal hemodynamic changes associated with the brain activity, it was found that the regional change in cerebral blood volume in the primary motor area overlaps the global change around the motor cortex. These results demonstrate that NIR topography can be used to effectively observe the human brain activity.

Spatial and temporal analysis of human motor activity using noninvasive NIR topography

Does the neonate's brain have left hemisphere (LH) dominance for speech? Twelve full-term neonates participated in an optical topography study designed to assess whether the neonate brain responds specifically to linguistic stimuli. Participants were tested with normal infant-directed speech, with the same utterances played in reverse and without auditory stimulation. We used a 24-channel optical topography device to assess changes in the concentration of total hemoglobin in response to auditory stimulation in 12 areas of the right hemisphere and 12 areas of the LH. We found that LH temporal areas showed significantly more activation when infants were exposed to normal speech than to backward speech or silence. We conclude that neonates are born with an LH superiority to process specific properties of speech.

/pdf/sounds-and-silence-an-optical-topography-study-of-language-y8l62fk0k0.pdf

Sounds and silence: An optical topography study of language recognition at birth

Studies of young infants are critical to understand perceptual, motor, and cognitive processing in humans. However, brain mechanisms involved are poorly understood, because the use of brain-imaging methods such as functional magnetic resonance imaging in awake infants is difficult. In the present study we show functional brain imaging of awake infants viewing visual stimuli by means of multichannel near-infrared spectroscopy, a technique that permits a measurement of cerebral hemoglobin oxygenation in response to brain activation through the intact skull without subject constraint. We found that event-related increases in oxyhemoglobin were evident in localized areas of the occipital cortex of infants aged 2–4 months in response to a brief presentation of a checkerboard pattern reversal while they maintained fixation to attention-grabbing stimuli. The dynamic change in cerebral blood oxygenation was qualitatively similar to that observed in the adult brain. This result introduces near-infrared optical topography as a method for investigating the functional development of the brain in early infancy.

https://www.pnas.org/content/pnas/100/19/10722.full.pdf

Atsushi Maki

Papers

Spatial and temporal analysis of human motor activity using noninvasive NIR topography

Sounds and silence: An optical topography study of language recognition at birth

Brain imaging in awake infants by near-infrared optical topography

Non-invasive assessment of language dominance with near-infrared spectroscopic mapping

Non-invasive functional mapping with multi-channel near infra-red spectroscopic topography in humans