Sniffing behaviour, or recognizing a lily by smell, but not recognizing a sock on sight

Disinhibition of olfaction: human olfactory performance improves following low levels of alcohol

We hypothesize that true human olfactory abilities are obscured by cortical inhibition. Alcohol reduces inhibition. We therefore tested the hypothesis that olfactory abilities will improve following alcohol consumption. We measured olfaction in 85 subjects, 45 in a between-subjects design, and 40 in a repeated-measures within-subjects design before and after consumption of alcoholic or non-alcoholic beverages. Subjects were also assessed using neurocognitive measures of inhibition. Following alcohol consumption, blood alcohol levels ranged from 0.005% to 0.11%. Across subjects, before any consumption of alcohol, we found that individuals who were less inhibited had lower (better) olfactory detection thresholds (r=0.68, p<0.005). Moreover, after alcohol consumption, subjects with low alcohol levels could make olfactory discriminations that subjects with 0% alcohol could not make (chance=33%, alcohol=51.3±22.7%, control=34.7±31.6%, t(43)=2.03, p<0.05). Within subjects, we found correlations between levels of alcohol and olfactory detection (r=0.63, p<0.005) and discrimination (r=-0.50, p<0.05), such that performance was improved at low levels of alcohol (significantly better than baseline for detection) and deteriorated at higher levels of alcohol. Finally, levels of alcohol-induced improved olfactory discrimination were correlated with levels of alcohol-induced cognitive disinhibition (r=0.48, p<0.05). Although we cannot rule out alternative non-inhibitory alcohol-induced routes of influence, we conclude that improved olfaction at low levels of alcohol supports the notion of an inhibitory mechanism obscuring true olfactory abilities.

Hyperlexia and ambient echolalia in a case of cerebral infarction of the left anterior cingulate cortex and corpus callosum

We report the case of a 69-year-old woman with cerebral infarction in the left anterior cingulate cortex and corpus callosum. She showed hyperlexia, which was a distinctive reading phenomenon, as well as ambient echolalia. Clinical features also included complex disorders such as visual groping, compulsive manipulation of tools, and callosal disconnection syndrome. She read words written on the cover of a book and repeated words emanating from unrelated conversations around her or from hospital announcements. The combination of these two features due to a focal lesion has never been reported previously. The supplementary motor area may control the execution of established subroutines according to external and internal inputs. Hyperlexia as well as the compulsive manipulation of tools could be interpreted as faulty inhibition of preexisting essentially intact motor subroutines by damage to the anterior cingulate cortex reciprocally interconnected with the supplementary motor area.

Fluctuating Kluver-Bucy syndrome in a child with epilepsy due to bilateral anterior temporal congenital malformations

An 11-year-old boy with epilepsy due to congenital bilateral anterior temporal lobe malformations presented with fluctuating Kluver-Bucy syndrome (KBS). Since the age of 2, he had experienced clusters of three or four daily complex partial seizures over 2-3 days in a month, followed by a seizure-free interval of 3-4 weeks. During the seizure-free period, the patient exhibited hyperorality, sniffing, irritability alternating with placidity, anxiety, unsolicited sexual gestures, and unusual calmness after eating. KBS features escalated up to the onset of the seizure cluster, and remitted after the seizures. Brain MRI revealed bilateral anterior temporal cortical dysplasia with enlarged and dysmorphic amygdalar-hippocampal complex. Brain [(18)F]fluorodeoxyglucose positron emission tomography PET showed bilateral anterior and mesial temporal hypometabolism. Video/EEG monitoring revealed independent right and left temporal lobe seizures. This is the first reported case of KBS due to congenital bitemporal malformations. Also, KBS behavior phenotype in this patient fluctuated, with escalation during the seizure-free period and remission induced by the monthly seizure cluster. This fluctuating pattern could represent forced normalization.

Emotions, behaviours and mood changes in stroke

The brain mediates and integrates all cognitive activities, emotional experiences and finally behaviours. Stroke is undoubtedly a privileged disease for human behavioural studies, because of its high incidence. Recent advances in high-resolution magnetic resonance imaging techniques and functional neuroimaging allow both the precise localization of lesions and on-line visualization of the activity of cerebral areas and networks. Nevertheless, the neuropsychiatry of stroke remains uncertain in its relationship with brain dysfunction. Clinical studies on registry populations, single case studies, and functional neuroimaging data provide interesting findings, but differences in methods and great individual intervariability still prevent a complete understanding of emotional perception and behavioural responses in stroke. We adopted an anatomical-functional model as an operational framework in order to systematize the recent literature on emotional, behavioural and mood changes after stroke. The dysfunction of the areas subserving fundamental and executive functions induces behavioural and affective changes (such as depression, anxiety, apathy) that reflect the dysfunction of the whole system. Conversely, lesions in the system of instrumental functions induce signature syndromes (aphasia, anosognosia). At any delay from stroke, the diagnosis and treatment of mood and behavioural changes are a priority for clinicians and healthcare professionals to improve the quality of life of patients.

The scented brain: pheromonal responses in humans

Using PET, Savic et al., in this issue of Neuron, found a sexually dimorphic neural response to two putative human pheromones. The specific regions activated combined with the pronounced sex difference depict a pheromonal-type brain response in humans. Here, we preview this finding and suggest that human pheromones exist.