Modular, cement-free, customized headpost and connector-chamber implants for macaques.

Background: Neurophysiological studies with awake macaques typically require chronic cranial implants. Headpost and connector-chamber implants are used to allow head stabilization and to house connectors of chronically implanted electrodes, respectively.

New Method: We present long-lasting, modular, cement-free headpost implants made of titanium that consist of two pieces: a baseplate and a top part.

Spontaneous variability in gamma dynamics described by a damped harmonic oscillator driven by noise.

Circuits of excitatory and inhibitory neurons generate gamma-rhythmic activity (30-80 Hz). Gamma-cycles show spontaneous variability in amplitude and duration. To investigate the mechanisms underlying this variability, we recorded local-field-potentials (LFPs) and spikes from awake macaque V1.

Predictive coding of natural images by V1 firing rates and rhythmic synchronization.

Predictive coding is an important candidate theory of self-supervised learning in the brain. Its central idea is that sensory responses result from comparisons between bottom-up inputs and contextual predictions, a process in which rates and synchronization may play distinct roles. We recorded from awake macaque V1 and developed a technique to quantify stimulus predictability for natural images based on self-supervised, generative neural networks.

Surface color and predictability determine contextual modulation of V1 firing and gamma oscillations.

The integration of direct bottom-up inputs with contextual information is a core feature of neocortical circuits. In area V1, neurons may reduce their firing rates when their receptive field input can be predicted by spatial context. Gamma-synchronized (30-80 Hz) firing may provide a complementary signal to rates, reflecting stronger synchronization between neuronal populations receiving mutually predictable inputs.

Effects of acute systemic and intra-cerebral stimulation of cannabinoid receptors on sensorimotor gating, locomotion and spatial memory in rats.

Rationale: Cannabinoid CB(1) receptors in the brain are targets of both endocannabinoid signalling and the psychoactive compounds of the hemp plant. They mediate neuronal effects of their ligands in various corticolimbic and striatal circuits by presynaptic regulation of transmitter release.

Objectives/methods: This study investigates acute systemic effects of the full CB(1) receptor agonist WIN 55,212-2 (WIN) on prepulse inhibition (PPI) of the acoustic startle response (ASR), locomotor activity and spatial memory retrieval in an eight-arm radial-maze task.