Just as hippocampal lesions are principally responsible for ‘temporal lobe’ amnesia, lesions affecting the anterior thalamic nuclei seem principally responsible for a similar loss of memory, ‘diencephalic’ amnesia. Compared to the former, the causes of diencephalic amnesia have remained elusive. A potential clue comes from how the two sites are interconnected, as within the hippocampal formation, only the subiculum has direct, reciprocal connections with the anterior thalamic nuclei. We found that both permanent and reversible anterior thalamic nuclei lesions in male rats cause a cessation of subicular spatial signalling, reduce spatial memory performance to chance, but leave hippocampal CA1 place cells largely unaffected. We suggest that a core element of diencephalic amnesia stems from the information loss in hippocampal output regions following anterior thalamic pathology. Significance Statement: At present, we know little about interactions between temporal lobe and diencephalic memory systems. Here...

Critical decisions, such as in domains ranging from medicine to finance, are often made under threatening circumstances that elicit stress and anxiety. The negative effects of such reactions on learning and decision-making have been repeatedly underscored. In contrast, here we show that perceived threat alters the process by which evidence is accumulated in a way that may be adaptive. Participants (n = 91) completed a sequential evidence sampling task in which they were incentivized to accurately judge whether they were in a desirable state, which was associated with greater rewards than losses, or an undesirable state, which was associated with greater losses than rewards. Prior to the task participants in the ‘threat group’ experienced a social-threat manipulation. Results show that perceived threat led to a reduction in the strength of evidence required to reach an undesirable judgement. Computational modelling revealed this was due to an increase in the relative rate by which negative information was a...

Substantia nigra pars compacta (SNc) dopaminergic (DA) neurons display a peculiar electrical phenotype characterized in vitro by a spontaneous tonic regular activity (pacemaking activity), a broad action potential and a biphasic post-inhibitory response. The transient A-type current (IA) is known to play a crucial role in this electrical phenotype, and so far this current was considered to be carried exclusively by Kv4.3 potassium channels. Using Kv4.3-/- transgenic mice, we demonstrate that the constitutive loss of this channel is associated with increased exploratory behavior and impaired motor learning at the behavioral level. Consistently it is also associated with a lack of compensatory changes in other ion currents at the cellular level. Using antigen retrieval immunohistochemistry, we then demonstrate that Kv4.2 potassium channels are also expressed in SNc DA neurons, even though their contribution to IA appears significant only in a minority of neurons (∼5-10%). Using correlative analysis on record...

Current models of object recognition are based on spatial representations build from object features that are simultaneously present in the retinal image. However, one can recognize an object when it moves behind a static occluder and only a small fragment of its shape is visible through a slit at a given moment in time. Such anorthoscopic perception requires spatio-temporal integration of the successively presented shape parts during slit-viewing. Human fMRI studies suggested that ventral visual stream areas represent whole shapes formed through temporal integration during anorthoscopic perception. To examine the time course of shape-selective responses during slit-viewing, we recorded the responses of single inferior temporal (IT) neurons of rhesus monkeys to moving shapes that were only partially visible through a static narrow slit. The IT neurons signaled shape identity by their response when that was cumulated across the duration of the shape presentation. Their shape preference during slit-viewing e...

The striatum is the main structure of the basal ganglia. The striatum receives inputs from various cortical areas, and its subregions play distinct roles in motor and emotional functions. Recently, striatal maps based on corticostriatal connectivity and striosome-matrix compartmentalization were developed, and we were able to subdivide the striatum into seven subregions. Dopaminergic modulation of the excitability of medium spiny neurons is critical for striatal function. In this study, we investigated the functional properties of dopamine signaling in seven subregions of the striatum from male mice. By monitoring the phosphorylation of PKA substrates including DARPP-32 in mouse striatal slices, we identified two subregions with low D1 receptor signaling: the dorsolateral portion of the intermediate/rostral part (DL-IR) and the intermediate/caudal part (IC). Low D1 receptor signaling in the two subregions was maintained by phosphodiesterase 10A and muscarinic M4 receptors. In an animal model of 6-OHDA-indu...

Although composing two words into a complex representation (e.g., “coffee cake”) is conceptually different from forming associations between a pair of words (e.g., “coffee, cake”), the brain regions supporting semantic composition have also been implicated for associative encoding. Here, we adopted a two-word magnetoencephalography (MEG) paradigm which varies compositionality (“French/Korean cheese” vs. “France/Korea cheese”) and strength of association (“France/French cheese” vs. “Korea/Korean cheese”) between the two words. We collected MEG data while 42 English speakers (24 females) viewed the two words successively in the scanner, and we applied both univariate regression analyses and multivariate pattern classification to the source estimates of the two words. We show that the left anterior and middle temporal lobe (LATL; LMTL) are distinctively modulated by semantic composition and semantic association. Specifically, the LATL is mostly sensitive to high-association compositional phrases, while the LM...

The non-psychoactive phytocannabinoid cannabidiol (CBD) has been shown to have analgesic effects in animal studies but little is known about its mechanism of action. We examined effects of CBD on intrinsic excitability of primary pain-sensing neurons. Studying acutely-dissociated capsaicin-sensitive mouse DRG neurons at 37°C, we found that CBD effectively inhibited repetitive action potential firing, from 15-20 action potentials evoked by 1-s current injections in control to 1-3 action potentials with 2 μM CBD. Reduction of repetitive firing was accompanied by reduction of action potential height, widening of action potentials, reduction of the afterhyperpolarization, and increased propensity to enter depolarization block. Voltage clamp experiments showed that CBD inhibited both TTX-sensitive (TTX-S) and TTX-resistant (TTX-R) sodium currents in a use-dependent manner. CBD showed strong state-dependent inhibition of TTX-R channels, with fast binding to inactivated channels during depolarizations and slow un...

The Russian fox-farm experiment is an unusually long-running and well-controlled study designed to replicate wolf-to-dog domestication. As such, it offers an unprecedented window onto the neural mechanisms governing the evolution of behavior. Here we report evolved changes to gray matter morphology resulting from selection for tameness vs. aggressive responses toward humans in a sample of 30 male fox brains. Contrasting with standing ideas on the effects of domestication on brain size, tame foxes did not show reduced brain volume. Rather, gray matter volume in both the tame and aggressive strains was increased relative to conventional farm foxes bred without deliberate selection on behavior. Furthermore, tame- and aggressive-enlarged regions overlapped substantially, including portions of motor, somatosensory, and prefrontal cortex, amygdala, hippocampus, and cerebellum. We also observed differential morphological covariation across distributed gray matter networks. In one prefrontal-cerebellum network, th...

The overexpression of calcineurin leads to astrocyte hyperactivation, neuronal death, and inflammation, which are characteristics often associated with pathologic aging and Alzheimer's disease. In this study, we tested the hypothesis that tacrolimus, a calcineurin inhibitor, prevents age-associated microstructural atrophy, which we measured using higher-order diffusion MRI, in the middle-aged beagle brain ( n = 30, male and female). We find that tacrolimus reduces hippocampal ( p = 0.001) and parahippocampal ( p = 0.002) neurite density index, as well as protects against an age-associated increase in the parahippocampal ( p = 0.007) orientation dispersion index. Tacrolimus also protects against an age-related decrease in fractional anisotropy in the prefrontal cortex ( p < 0.0001). We also show that these microstructural alterations precede cognitive decline and gross atrophy. These results support the idea that calcineurin inhibitors may have the potential to prevent aging-related pathology if administere...

Forrest Gump or The Matrix ? Preference-based decisions are subjective and entail self-reflection. However, these self-related features are unaccounted for by known neural mechanisms of valuation and choice. Self-related processes have been linked to a basic interoceptive biological mechanism, the neural monitoring of heartbeats, in particular in ventromedial prefrontal cortex (vmPFC), a region also involved in value encoding. We thus hypothesized a functional coupling between the neural monitoring of heartbeats and the precision of value encoding in vmPFC. Human participants of both sexes were presented with pairs of movie titles. They indicated either which movie they preferred or performed a control objective visual discrimination that did not require self-reflection. Using magnetoencephalography, we measured heartbeat-evoked responses (HERs) before option presentation and confirmed that HERs in vmPFC were larger when preparing for the subjective, self-related task. We retrieved the expected cortical va...