This exploratory project will evaluate the usefulness of a newly developed instrument called baby SQUID for assessing brain functions in human infants. The baby SQUID is a high-resolution magnetoencephalography (MEG) system designed to detect cortical activity in infants with an unprecedented level of sensitivity and spatial resolution. An array of 76 MEG sensors can be placed 6 mm from the scalp, rather than -20 mm as in conventional MEGs. Since the combined thickness of scalp and skull is -4 mm in neonates, MEG signals can be measured at 10 mm, rather than 25 mm, from brain surface. Since MEG signals fall off as a square of distance, they should be as much as 5 times stronger for the baby SQUID compared to conventional MEG systems. In the next phase of development, the gap will be reduced from 6 mm to 3 mm so that the signals would be about 10 times stronger. The spatial resolution is about 3-4 times higher than the conventional systems because of the smaller gap and higher sensor density (12-14 mm channel spacing instead of 30-40 mm for adult MEGs). Preliminary results show that spontaneous activity can be measured clearly with high SNR and evoked activity can be measured with very little signal averaging from healthy infants. Unlike EEG, MEG signals are not distorted by the fontanels and sutures in the skull. This property of MEG greatly simplifies the interpretation of the signals. Due to these characteristics of MEG and baby SQUID, it is possible to perform a cortical current imaging (CCI). Instead of the dipole approach, our simulation study shows that the baby SQUID provides images of the cortical neuronal current distribution. We propose to use the CCI to determine cortical activity in healthy infants and infants with cerebral palsy (CP) and with neocortical epilepsy.
Aim 1 will characterize the spontaneous activity from different regions of the brain with a focus on elucidating the basis of localized spindles seen in healthy babies. We predict that the generators can be identified due to the high sensitivity and spatial resolution.
Aim 2 will measure spontaneous and somatically evoked activity in CP infants with hemiparesis. The evoked response will localize the projection areas of different parts of the body. Preliminary studies have shown a profound level of plasticity in both the affected and unaffected cortices. We predict that the spontaneous activity from these specific projection areas, identified by the CCI, is abnormal in the unaffected as well as affected side.
Aim 3 will measure the epileptiform activity in infants with neocortical epilepsy. We predict that the CCI will be able to distinguish functionally discrete areas in the zone producing the spikes. Human brain development is an area of biomedical research that is still in its infancy because of difficulties in finding tools that are safe and yet powerful. We believe that this project, if successful, will open new windows into brain development in healthy infants as well as infants with various neurological disorders. ? ? ?
| Berchicci, M; Zhang, T; Romero, L et al. (2011) Development of mu rhythm in infants and preschool children. Dev Neurosci 33:130-43 |
