Familiarity-related neuronal responses under normal conditions and in an animal model of mental illness

Recognition memory is one of the most basic types of memory. One type of recognition memory is visual familiarity, which is the sense that a visual stimulus has been encountered before. This type of memory is affected in different mental illnesses, like schizophrenia and autism. The perirhinal cortex, which is a part of the medial temporal lobe has long been believed to be crucial for recognition. This work had 2 main lines of research. The first part, described in chapters Chapter 3 and Chapter 4 , set out to investigate whether activity at either the population level or at the single-unit level in the mouse perirhinal cortex was correlated with visual familiarity. In these chapters, the recordings were made also in the visual cortex and the hippocampus to put the perirhinal response in the context of the activity both upstream and downstream from it, respectively. Visual stimuli evoked responses in the perirhinal cortex, no familiarity-related modulation could be detected at both levels of analysis. That was true even when the visual cortex demonstrated familiarity-related differences in response. The second part of the work, described in chapters Chapter 5 and Chapter 6 examined the mice with haplo-insufficiency of the CYFIP1 gene as a possible new model for mental illness. First, the animal’s validity as a model of mentalillness was tested using auditory-evoked potential, one of the most ubiquitous phenomena that appears with mental illness in people and animal models. Then, recognition memory and the neuronal activity in the perirhinal and the visual cortex was tested, to see if they demonstrate other symptoms relating to schizophrenia. In the second line of work, the CYFIP1 mice demonstrated an auditory-evoked potential profile more like that observed in fragile-X syndrome, rather than schizophrenia and did not present any changes in both recognition memory or the electrical activity in the visual and the perirhinal cortex. This work showed that the perirhinal cortex does not show any familiarity-related activity unlike the current assumption in the literature. It also showed that the CYFIP1 mice might be a possible model for autism and Fragile-X syndrome

GABAergic circuits reflect different requirements for sensory integration in postnatal mouse neocortex

Information transfer in mammalian cerebral cortex is dependent on GABAergic interneuron circuits that are widely assumed to be uniform across neocortex. Here we demonstrate that this does not hold true during postnatal life prior to the onset of active sensory exploration in mice. During this time, somatostatin interneurons differentially contribute to sensory-evoked activity in primary somatosensory (S1BF) and visual (V1) cortices. In S1BF, somatostatin interneurons provide a mechanism for feed-forward control of sensory responses as opposed to the feed-back role observed in V1. This functional divergence is explained by differences in both somatostatin subtype and the transient circuits formed by these cells. We propose that the somatosensory circuit represents an adaptation to control early touch information, a key sense for neonatal mice. Further, the presence of distinct, area-dependent GABAergic circuits suggests divergent genetic/molecular programs across different cortices, adding further complexity to our endeavors to understand the etiology of neurodevelopmental psychiatric disorders

Acute periodontal lesions

This is a review and update on acute conditions affecting the gingival tissues, including abscesses in the periodontium, necrotizing periodontal diseases, and other acute conditions that cause gingival lesions with acute presentation, such as infectious process not associated with oral bacterial biofilms, muco-cutanenous disorders, and traumatic and allergic lesions. A periodontal abscess is clinically important since it is a relatively frequent dental emergency, it can compromise the periodontal prognosis of the affected tooth, and because bacteria within the abscess have been identified, mainly by the type of etiology, and there are clear diffrences between those affecting a previously existing periodontal pocket ahd those affecting healthy sites. Therapy for this acute condition consists of drainage and tissue debridement, with individual evaluation of the need for systemic antimicrobial therapy. the definitive treatment of the pre-existing condition should be accomplished after the acute phase is controlled. Necrotizing periodontal disease (NPD) present three typical clinical features : papilla necrosis, gingival bleeding, and pain. Although the prevalence of these diseases is not high, their importance is clear, since they represent the most severe conditions associated with dental biofilm, with very rapid tissue destruction. In adittion to bacteria, the etiology of NPD includes numerous factors that alter the host response and predispose to these diseases, including HIV infection, malnutrition, stress, and tobacco smoking. The treatment consists of superficial debridement, careful mechanical oral hygiene, rinsing with chlorhexidine, and daily re-evaluation. Systemic antimicrobials may be used adjunctively in severe cases or in non-responding conditions and the best option is metronidazole.Once the acute disease is under control, definitive treatment should be provided, including the adequate therapy for the pre-existing gingivitis or periodontitis. Among other acute conditions affecting the periodontal tissues, but not caused by the microorganisms present in oral biofilms , are infectious diseases, muco-cutaneous diseases and traumatic or allergic lesions. In most cases, the gingival envolvement is not severe, though they are common and may prompt a dental emergency visit. These conditions may the direct result of a trauma or the consequence of the breaking of vesicles and bullae. A proper differential diagnosis is important for an adequate management of the case

Absence of neuronal response modulation with familiarity in perirhinal cortex

The perirhinal cortex (PRH) is considered a crucial cortical area for familiarity memory and electrophysiological studies have reported the presence of visual familiarity encoding neurons in PRH. However, recent evidence has questioned the existence of these neurons. Here, we used a visual task in which head-restrained mice were passively exposed to oriented gratings or natural images. Evoked potentials and single-unit recordings showed evoked responses to novelty in V1 under some conditions. However, the PRH showed no response modulation with respect to familiarity under a variety of different conditions or retention delays. These results indicate that the PRH does not contribute to familiarity/novelty encoding using passively exposed visual stimuli

GABAergic circuits reflect different requirements for emergent perception in postnatal mouse neocortex

Information transfer in the mammalian cerebral cortex is dependent on locally-projecting GABAergic interneuron circuits that are widely assumed to be uniform across neocortical areas. We demonstrate that this does not hold true during the highly dynamic period of postnatal life prior to the onset of active sensory exploration. During this time, a subset of interneuron defined by expression of the neuropeptide somatostatin differentially contribute to sensory-evoked activity in primary somatosensory and visual cortices. This functional divergence between the two areas is explained by differences in the composition of somatostatin interneuron subtypes and the transient circuits formed by these cells; the somatosensory circuit representing an adaptation to control early neonatal touch information. Understanding such area-dependent differences will promote our endeavours to understand the aetiology of developmental psychiatric disorders

Cutaneous lesions of the external ear

Skin diseases on the external aspect of the ear are seen in a variety of medical disciplines. Dermatologists, othorhinolaryngologists, general practitioners, general and plastic surgeons are regularly consulted regarding cutaneous lesions on the ear