Dose-dependent changes in orientation amplitude maps in the cat visual cortex after propofol bolus injections.

A general intravenous anesthetic propofol (2,6-diisopropylphenol) is widely used in clinical, veterinary practice and animal experiments. It activates gamma- aminobutyric acid (GABAa) receptors. Though the cerebral cortex is one of the major targets of propofol action, no study of dose dependency of propofol action on cat visual cortex was performed yet.

Adaptive behavior of neighboring neurons during adaptation-induced plasticity of orientation tuning in VI.

Background: Sensory neurons display transient changes of their response properties following prolonged exposure to an appropriate stimulus (adaptation). In adult cat primary visual cortex, orientation-selective neurons shift their preferred orientation after being adapted to a non-preferred orientation. The direction of those shifts, towards (attractive) or away (repulsive) from the adapter depends mostly on adaptation duration.

Visual cells remember earlier applied target: plasticity of orientation selectivity.

Background: A canonical proposition states that, in mature brain, neurons responsive to sensory stimuli are tuned to specific properties installed shortly after birth. It is amply demonstrated that that neurons in adult visual cortex of cats are orientation-selective that is they respond with the highest firing rates to preferred oriented stimuli.

Methodology/principal Findings: In anesthetized cats, prepared in a conventional fashion for single cell recordings, the present investigation shows that presenting a stimulus uninterruptedly at a non-preferred orientation for twelve minutes induces changes in orientation preference.

Synchrony between orientation-selective neurons is modulated during adaptation-induced plasticity in cat visual cortex.

Background: Visual neurons respond essentially to luminance variations occurring within their receptive fields. In primary visual cortex, each neuron is a filter for stimulus features such as orientation, motion direction and velocity, with the appropriate combination of features eliciting maximal firing rate. Temporal correlation of spike trains was proposed as a potential code for linking the neuronal responses evoked by various features of a same object.

Spatial frequency characteristics of nearby neurons in cats' visual cortex.

Various methods have allowed mapping of responses to several stimulus features on the cortical surface, particularly edge orientation and motion direction. The cortical mapping of spatial frequencies (SF), which is the basic property that leads to perception of spatial details of visual objects, is still controversial. We recorded simultaneously extracellular action potentials from neighboring cells in superficial layers of the area 17-18 border region of anesthetized cats.

Neuron participation in a synchrony-encoding assembly.

Background: Synchronization of action potentials between neurons is considered to be an encoding process that allows the grouping of various and multiple features of an image leading to a coherent perception. How this coding neuronal assembly is configured is debated. We have previously shown that the magnitude of synchronization between excited neurons is stimulus-dependent.

Analysis of frequency components of cortical potentials evoked by progressive misalignment of Kanizsa squares.

Cortical gamma oscillations (20-100 Hz) are thought to play an important role in encoding visual perception. If so they should emerge at about threshold. In the present investigation we examined the latter proposal.

Influence of NO downregulation on oscillatory evoked responses in developing rat superior colliculus.

Nitric oxide (NO) is involved in neuronal transmission by modulating neurotransmitter release in adults and in stabilizing synaptic connections in developing brains. We investigated the influence of downregulation of NO synthesis on oscillatory components of ON and OFF evoked field potentials in the rat superior colliculus. NO synthesis was decreased by inhibiting nitric oxide synthase (NOS) with an acute microinjection of N(omega)-nitro-L-arginine methyl ester (L-NAME).