Neurologists were the first to record a stationary auditory evoked potentials from human fetuses aged 30-39 weeks, reported in PLoS ONE. They determined what state — tranquil or active — such capacities are easier to detect, and suggested that analysis of such potentials in children for a few weeks before the birth, it will be possible to monitor the degree of development of their auditory cortex.
The human ear can be checked with a set of listening tests where he will need to answer certain questions, to point out the differences between sounds if they are, and so on. If the subject cannot or doesn’t want to talk or something by his behavior to react to the test stimuli, it is possible to use methods of check of activity of the brain, primarily electroencephalography (EEG) and magnetoencephalography (MEG). Their temporal and spatial resolution sufficient to identify which areas of the brain activated in response to the occurrence of a specific sound — at least, if this sound to present multiple times and watch while evoked potentials.
The brain response to audioscale different tonalities depend on the state of the auditory cortex. If some structure has not formed, then the evoked potentials in response to several common stimuli will not occur, will appear with different latency (that is, after some “non-standard” time from the moment when he was enjoyed the sound) or I will have somehow changed. This fact could be used to study the development of the auditory cortex in the human fetus in the later stages of development.
One of the variants of the auditory evoked potentials, transient event-related (transient auditory event related response, AERR), already recorded from unborn children in response to single pure tones. And auditory evoked potentials of a different type, stationary (auditory steady-state response, ASSR), people before birth have not yet studied.
Melbourne Nipple (Dorothea Niepel) from the University clinic of tübingen and her colleagues from Germany and the United States have conducted a pilot study which conducted 47 sessions magnetoencephalography for 24 pregnant women, who during pregnancy have not observed any health problems. Some of them held two or three sessions MEG, so the number of sessions does not match the number of subjects. Yet unborn children of these women were divided into three groups according to the period of fetal development: 30-32 weeks 33-35 weeks 36-39 weeks.
In one session, the fruits of randomly presented audio stimulus with a height of 27 or 42 Hertz to 500 Hertz noise. Their volume was 94 decibels at the surface of the abdomen, and in passing through tissues, as scientists believe, was lost no more than 20-30 decibels. Each stimulus lasted a second, and the interval between sounds was either 3 or 3.5 seconds. The experiment lasted no more than 10 minutes, and during this time the unborn child could hear sounds from 80-100. In parallel, scientists have recorded magnetoencephalogram and magnetocardiogram of the fetus. Latest allowed to find out about his condition. The fetus is over 32 weeks on the activity of the heart can distinguish four States (active and passive sleep and Wake), those who are younger, only two — passive and active.