Optical imaging of neuronal activity.
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Animals↗
Biomedical subjects
R D Frostig
Publications and source records attributed to R D Frostig.
Analysis of frequency components in time series data.
We describe a method for assessing the periodic elements of variations in a time series and illustrate it with examples drawn from infant cardiac beat-to-beat intervals. Compared with averaging techniques, the procedure has the advantage of providing quantification of periodical elements in a non-stationary time series. Moreover, the procedure is robust to artifacts such as those which frequently contaminate beat-to-beat interval data. The method examines successive increments of the time-series plot, and when they become negative or positive, peaks and troughs are noted in the curve. Two successive troughs confine a wave which may be described by its amplitude and period. The set of all waves, terminated by the sequence of troughs, is defined as the "high-frequency component" of the series. Waves of the next low-frequency component are delineated when only the high-frequency peaks (or troughs) are considered. Thus, low-frequency peaks are defined as peaks of the curve formed by the high-frequency peaks, and lower-frequency troughs are the troughs of the curve formed by the high-frequency troughs. The process iterates to assess variations at lower and lower frequencies and any specific frequency component is being characterized by the median and interquartile range of its wave amplitudes and wave periods.
Heart Rate↗
Information trains. The technique and its uses in spike train and network analysis, with examples taken from the nucleus parabrachialis medialis during sleep-waking states.
We describe an analytical procedure for assessing functional interactions between neuronal spike trains based on the outcome of cross-correlation procedures. Subsets of a reference cell spike train in a two-train recording are extracted, based on their time-locked relationship to spikes in the dependent train. Such timing relationships comprise the significant primary structures in the cross-correlogram. Different subsets can be extracted for different primary structures in the same correlogram (i.e. a subset responsible for an interaction effect, a subset responsible for a shared input effect, etc.). These new spike trains represent an information transfer process across synapses. These 'information trains' may be compared and correlated to different cells of the network across different functional conditions such as sleep-waking states, and may also be subjected to conventional spike train analysis techniques such as rate histogram, auto-correlation and cross-correlation procedures. We illustrate the information train procedures with a network analysis of a set of cells recorded in the nucleus parabrachialis medialis during different sleep-waking states.
Action Potentials↗
The effects of stimuli on the activity and functional connectivity of local neuronal groups in the cat auditory cortex.
Simultaneous extracellular recordings from one electrode of 'local' groups of 3-6 neurons were obtained from the auditory cortex of unanesthetized, paralyzed cats. The activity and functional connectivity of local microenvironments were examined under various auditory stimuli. Single cell response patterns were examined using peri-stimulus (PST) histograms and functional connectivity among neighboring cells by the cross renewal density (CRD) histograms. Analysis of the PST histograms suggested that a high percentage of single cells demonstrated different response patterns to different stimuli. Analysis of the CRD histograms suggested, on the one hand, that only small numbers of neighboring cells behaved as if there were direct connections from one cell to another, and that these direct connections appeared to be excitatory. On the other hand, many cell pairs shared input from shared sources which lay outside the local groups. The majority of functional connections were altered by at least one of the stimuli delivered, thus demonstrating the system's plasticity. It is suggested that long-term gates at the synaptic level are responsible for this phenomenon.
Action Potentials↗
Functional architecture of cortex revealed by optical imaging of intrinsic signals.
Optical imaging of cortical activity offers several advantages over conventional electrophysiological and anatomical techniques. One can map a relatively large region, obtain successive maps to different stimuli in the same cortical area and follow variations in response over time. In the intact mammalian brain this imaging has been accomplished with the aid of voltage sensitive dyes. However, it has been known for many years that some intrinsic changes in the optical properties of the tissue are dependent on electrical or metabolic activity. Here we show that these changes can be used to study the functional architecture of cortex. Optical maps of whisker barrels in the rat and the orientation columns in the cat visual cortex, obtained by reflection measurements of the intrinsic signal, were confirmed with voltage sensitive dyes or by electrophysiological recordings. In addition, we describe an intrinsic signal originating from small arteries which can be used to investigate the communication between local neuronal activity and the microvasculature. One advantage of the method is that it is non-invasive and does not require dyes, a clear benefit for clinical applications.
Animals↗
Suprathreshold auditory cortex activation visualized by intrinsic signal optical imaging.
The suprathreshold tonotopic organization of rat and guinea pig auditory cortex was investigated using intrinsic signal optical imaging through a thinned skull. Optical imaging revealed that suprathreshold pure sine wave tone stimulation (25-80 dB) evoked activity over large cortical areas that were tonotopically organized. Three-dimensional surface plots of the activated areas revealed "patchy' auditory-evoked activity consisting of numerous local peaks and valleys building to a maximum. Subsequent detailed electrophysiological mapping in the same subjects confirmed the localization of auditory-evoked activity based on optical imaging, including responses to a test frequency at cortical loci more than 2 octaves away from the threshold-defined isofrequency contour. The success of this technique in visualizing auditory cortex functional organization at suprathreshold stimulus levels will allow for future investigations of auditory cortex frequency representation, including representational plasticity induced by a variety of experimental manipulations.
Acoustic Stimulation↗