Dynamic characteristics of visual evoked potentials in the dog. I. Cortical and subcortical potentials evoked by sine wave modulated light.
ABSTRACT 1.1. Potentials evoked by sinusoidally modulated light (SML) were recorded from the lateral geniculate nucleus and occipital cortex of unanaesthetized dogs. The evoked potentials were analysed by discrete Fourier analysis.2.2. The harmonic components of SML evoked potentials were described by frequency response functions. The range of linear and non-linear behaviour was determined.3.3. A linear description was only possible regarding the SML evoked potentials recorded from the posterior marginal gyrus.4.4. Three types of non-linearities were characterized: saturation, non-linear oscillations responsible for the generation of subharmonics and essential non-linearities.5.5. The essential non-linearities correspond to rectification occurring in “on” and “off” neuronal populations; they were the dominant features of SML evoked potentials in the lateral geniculate nucleus and the calcarine region of occipital cortex, but not in the posterior marginal gyrus.6.6. The phase functions were shown to be determined in part by a delay time.7.7. The relations between SML evoked potential parameters and data obtained at the unit level are discussed.Résumé1.1. Les potentiels évoqués par une lumière modulée sinusoïdalement (LMS) ont été enregistrés au niveau du noyau géniculé latéral et du cortex occipital chez des chiens non-anesthésiés. Les potentiels évoqués ont été analysés par l'analyse de Fourier discrète.2.2. Les composantes harmoniques des potentiels évoqués par la LMS sont décrits par des fonctions amplitude/fréquence. La marge de comportement linéaire et non-linéaire est déterminée.3.3. Une description linéaire n'est possible que pour les potentiels évoqués par LMS enregistrés au niveau du gyrus marginal postérieur.4.4. Trois types de non-linéarité ont été définis: saturation, oscillation non-linéaire responsable de la production de sousharmoniques et non-linéarité essentielle.5.5. Les non-linéarités essentielles correspondent à une rectification survenant dans les populations neuroniques “on” et “off” ;elles constituent les données dominantes des potentiels évoqués par LMS dans le noyau géniculé latéral et la région calcarine du cortex occipital mais non dans le gyrus marginal postérieur.6.6. Les fonctions de phase se montrent déterminées partiellement par un temps de délai.7.7. Les relations entre les paramètres des potentiels évoqués par LMS et les données obtenues au niveau unitaire sont discutées.
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ABSTRACT: Speech comprehension relies on temporal cues contained in the speech envelope, and the auditory cortex has been implicated as playing a critical role in encoding this temporal information. We investigated auditory cortical responses to speech stimuli in subjects undergoing invasive electrophysiological monitoring for pharmacologically refractory epilepsy. Recordings were made from multicontact electrodes implanted in Heschl's gyrus (HG). Speech sentences, time compressed from 0.75 to 0.20 of natural speaking rate, elicited average evoked potentials (AEPs) and increases in event-related band power (ERBP) of cortical high-frequency (70-250 Hz) activity. Cortex of posteromedial HG, the presumed core of human auditory cortex, represented the envelope of speech stimuli in the AEP and ERBP. Envelope following in ERBP, but not in AEP, was evident in both language-dominant and -nondominant hemispheres for relatively high degrees of compression where speech was not comprehensible. Compared to posteromedial HG, responses from anterolateral HG-an auditory belt field-exhibited longer latencies, lower amplitudes, and little or no time locking to the speech envelope. The ability of the core auditory cortex to follow the temporal speech envelope over a wide range of speaking rates leads us to conclude that such capacity in itself is not a limiting factor for speech comprehension.Journal of Neuroscience 12/2009; 29(49):15564-74. · 6.91 Impact Factor
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ABSTRACT: Previously, social and cognitive abilities of dogs have been studied within behavioral experiments, but the neural processing underlying the cognitive events remains to be clarified. Here, we employed completely non-invasive scalp-electroencephalography in studying the neural correlates of the visual cognition of dogs. We measured visual event-related potentials (ERPs) of eight dogs while they observed images of dog and human faces presented on a computer screen. The dogs were trained to lie still with positive operant conditioning, and they were neither mechanically restrained nor sedated during the measurements. The ERPs corresponding to early visual processing of dogs were detectable at 75-100 ms from the stimulus onset in individual dogs, and the group-level data of the 8 dogs differed significantly from zero bilaterally at around 75 ms at the most posterior sensors. Additionally, we detected differences between the responses to human and dog faces in the posterior sensors at 75-100 ms and in the anterior sensors at 350-400 ms. To our knowledge, this is the first illustration of completely non-invasively measured visual brain responses both in individual dogs and within a group-level study, using ecologically valid visual stimuli. The results of the present study validate the feasibility of non-invasive ERP measurements in studies with dogs, and the study is expected to pave the way for further neurocognitive studies in dogs.Animal Cognition 04/2013; · 2.71 Impact Factor
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ABSTRACT: Studying cognition of domestic dogs has gone through a renaissance within the last decades. However, although the behavioral studies of dogs are beginning to be common in the field of animal cognition, the neural events underlying cognition remain unknown. Here, we employed a non-invasive electroencephalography, with adhesive electrodes attached to the top of the skin, to measure brain activity of from 8 domestic dogs (Canis familiaris) while they stayed still to observe photos of dog and human faces. Spontaneous oscillatory activity of the dogs, peaking in the sensors over the parieto-occipital cortex, was suppressed statistically significantly during visual task compared with resting activity at the frequency of 15-30 Hz. Moreover, a stimulus-induced low-frequency (∼2-6 Hz) suppression locked to the stimulus onset was evident at the frontal sensors, possibly reflecting a motor rhythm guiding the exploratory eye movements. The results suggest task-related reactivity of the macroscopic oscillatory activity in the dog brain. To our knowledge, the study is the first to reveal non-invasively measured reactivity of brain electrophysiological oscillations in healthy dogs, and it has been based purely on positive operant conditional training, without the need for movement restriction or medication.PLoS ONE 01/2013; 8(5):e61818. · 3.73 Impact Factor