A Methodology for Detecting Field Potentials from the External Ear Canal: NEER and EVestG

An algorithm called the neural event extraction routine (NEER) and a method called Electrovestibulography (EVestG) for extracting field potentials (FPs) from artefact rich and noisy ear canal recordings is presented. Averaged FP waveforms can be used to aid detection of acoustic and or vestibular pathologies. FPs were recorded in the external ear canal proximal to the ear drum. These FPs were extracted using an algorithm called NEER. NEER utilises a modified complex Morlet wavelet analysis of phase change across multiple scales and a template matching (matched filter) methodology to detect FPs buried in noise and biological and environmental artefacts. Initial simulation with simulated FPs shows NEER detects FPs down to −30 dB SNR (power) but only 13–23% of those at SNR’s <−6 dB. This was deemed applicable to longer duration recordings wherein averaging could be applied as many FPs are present. NEER was applied to detect both spontaneous and whole body tilt evoked FPs. By subtracting the averaged tilt FP response from the averaged spontaneous FP response it is believed this difference is more representative of the vestibular response. Significant difference (p < 0.05) between up and down whole body (supine and sitting) movements was achieved. Pathologic and physiologic evidence in support of a vestibular and acoustic origin is also presented

On the way to large-scale and high-resolution brain-chip interfacing

Brain-chip-interfaces (BCHIs) are hybrid entities where chips and nerve cells establish a close physical interaction allowing the transfer of information in one or both directions. Typical examples are represented by multi-site-recording chips interfaced to cultured neurons, cultured/acute brain slices, or implanted “in vivo”. This paper provides an overview on recent achievements in our laboratory in the field of BCHIs leading to enhancement of signals transmission from nerve cells to chip or from chip to nerve cells with an emphasis on in vivo interfacing, either in terms of signal-to-noise ratio or of spatiotemporal resolution. Oxide-insulated chips featuring large-scale and high-resolution arrays of stimulation and recording elements are presented as a promising technology for high spatiotemporal resolution interfacing, as recently demonstrated by recordings obtained from hippocampal slices and brain cortex in implanted animals. Finally, we report on an automated tool for processing and analysis of acquired signals by BCHIs

Gating in the spino-olivocerebellar pathways to the c1 zone of the cerebellar cortex during locomotion in the cat.

1. The field potentials evoked in the cerebellar cortical c1 zone by single-pulse, non-noxious stimulation of the superficial radial nerve have been recorded with tungsten-in-glass microelectrodes in awake cats. Responses that were due to transmission in the spino-olivocerebellar pathways (SOCPs), which terminate in the cortex as climbing fibres, were identified and studied while the cat walked on a moving belt. 2. The size of the climbing fibre-evoked potentials varied systematically during the step cycle. They were invariably largest in mid- to late swing of the ipsilateral forelimb and, at most recording sites (5/6), they were smallest during the first half of stance. 3. With low stimulus strength, the probability of evoking a measurable response also varied. The probability was greatest in mid- to late swing and least in early stance. 4. Similar variations were shown to occur when the analysis was restricted to responses evoked by a single functionally homogenous SOCP, the dorsal funiculus SOCP. 5. It is proposed that these variations reflect the operation of a gating mechanism which modulates the excitability of the SOCPs and prevents them transmitting self-generated tactile inputs to the cerebellum while facilitating transmission when unexpected inputs are most likely to arise. 6. The present data are compared with those from a similar study of the c2 zone SOCPs (Apps, Lidierth & Armstrong, 1990) and are discussed in relation to a study of the effects of unexpected mechanical perturbations of stepping (Andersson & Armstrong, 1987)