Visual recognition is heralded by shifts in local field potential oscillations and inhibitory networks in primary visual cortex.

Learning to recognize and filter familiar, irrelevant sensory stimuli eases the computational burden on the cerebral cortex. Inhibition is a candidate mechanism in this filtration process, and oscillations in the cortical local field potential (LFP) serve as markers of the engagement of different inhibitory neurons. We show here that LFP oscillatory activity in visual cortex is profoundly altered as male and female mice learn to recognize an oriented grating stimulus-low frequency (∼15 Hz peak) power sharply increases while high frequency (∼65 Hz peak) power decreases. These changes report recognition of the familiar pattern, as they disappear when the stimulus is rotated to a novel orientation. Two-photon imaging of neuronal activity reveals that parvalbumin-expressing inhibitory neurons disengage with familiar stimuli and reactivate to novelty, whereas somatostatin-expressing inhibitory neurons show opposing activity patterns. We propose a model in which the balance of two interacting interneuron circuits shifts as novel stimuli become familiar.SIGNIFICANCE STATEMENT:Habituation, familiarity and novelty detection are fundamental cognitive processes that enable organisms to adaptively filter meaningless stimuli and focus attention on potentially important elements of their environment. We have shown that this process can be studied fruitfully in the mouse primary visual cortex by using simple grating stimuli for which novelty and familiarity are defined by orientation, and by measuring stimulus-evoked and continuous local field potentials. Altered event-related and spontaneous potentials, and deficient habituation, are well-documented features of several neurodevelopmental psychiatric disorders. The paradigm described here will be valuable to interrogate the origins of these signals and the meaning of their disruption more deeply.

Stimulus-Selective Response Plasticity in Primary Visual Cortex: Progress and Puzzles.

Stimulus-selective response plasticity (SRP) is a robust and lasting modification of primary visual cortex (V1) that occurs in response to exposure to novel visual stimuli. It is readily observed as a pronounced increase in the magnitude of visual evoked potentials (VEPs) recorded in response to phase-reversing grating stimuli in neocortical layer 4. The expression of SRP at the individual neuron level is equally robust, but the qualities vary depending on the neuronal type and how activity is measured. This form of plasticity is highly selective for stimulus features such as stimulus orientation, spatial frequency, and contrast. Several key insights into the significance and underlying mechanisms of SRP have recently been made. First, it occurs concomitantly and shares core mechanisms with behavioral habituation, indicating that SRP reflects the formation of long-term familiarity that can support recognition of innocuous stimuli. Second, SRP does not manifest within a recording session but only emerges after an off-line period of several hours that includes sleep. Third, SRP requires not only canonical molecular mechanisms of Hebbian synaptic plasticity within V1, but also the opposing engagement of two key subclasses of cortical inhibitory neuron: the parvalbumin- and somatostatin-expressing GABAergic interneurons. Fourth, pronounced shifts in the power of cortical oscillations from high frequency (gamma) to low frequency (alpha/beta) oscillations provide respective readouts of the engagement of these inhibitory neuronal subtypes following familiarization. In this article we will discuss the implications of these findings and the outstanding questions that remain to gain a deeper understanding of this striking form of experience-dependent plasticity.

Concurrent transperitoneal repair for incidentally detected inguinal hernias during robotically assisted radical prostatectomy.

OBJECTIVE: To report our experience with concurrent intraperitoneal inguinal herniorrhaphy using prosthetic mesh during robotically assisted radical prostatectomy (RARP) for incidentally discovered inguinal hernias. METHODS: We performed a retrospective review of 1118 consecutive RARPs performed by one surgeon between July 2005 and July 2011. Cases that included concurrent hernia repair were compared with a group of patients matched 1:1 for age, body mass index, and year of surgery, who underwent RARP alone (controls). RESULTS: A total of 91 patients underwent 113 concurrent inguinal hernia repairs during RARP. Twenty-two patients (24%) underwent bilateral repair. Of the 69 patients undergoing unilateral repair, 41 (45%) underwent left-sided repair, and 29 (31%) underwent right-sided repair. Thirty-five (38%) patients had previous inguinal hernia repair. Body mass index of cases and controls were 27.5 ± 3.4 and 27.8 ± 3.1 kg/m(2), respectively. Mean operative time in cases was 185 ± 28 minutes vs 168 ± 31 minutes in controls (P <.001). Estimated blood loss was 170 ± 61 mL for cases vs 194 ± 82 mL for controls (P = .03). No differences were observed in length of stay or prevalence of postoperative complications. There was 1 hernia recurrence, which necessitated repeat repair 1 year after surgery. No mesh infections or other complications related to hernia repairs were observed. CONCLUSION: Inguinal hernias are a common intraoperative finding during RARP. Concurrent repair appears safe and effective with only a slight increase in operative time, and no increase in morbidity.