Hippocampal dependent neuropsychological tests and their relationship to measures of cardiac and self-report interoception

Interoception, Affect, and Cognition in Older Adults

Interoception is the detection of signals that arise from within the body. Interoceptive sensitivity has been found to be associated with affect and cognition among younger adults, and examination of these relationships in older adult samples is beginning to emerge. Here, we take an exploratory approach to determine how demographic, affective, and cognitive variables relate to interoceptive sensitivity in neurologically normal older adults, aged 60-91 years old. Ninety-one participants completed a comprehensive neuropsychological battery, self-report questionnaires, and a heartbeat counting task to measure interoceptive sensitivity. Our findings revealed several relationships: 1) interoceptive sensitivity was inversely correlated with measures of positive emotionality: participants with higher interoceptive sensitivity tended to have lower levels of positive affect and trait extraversion; 2) interoceptive sensitivity was found to positively correlate with cognition: participants who performed better on the heartbeat-counting task also tended to perform better on a measure of delayed verbal memory; and 3) when examining the predictors of interoceptive sensitivity in a single hierarchical regression model, higher interoceptive sensitivity was related to: higher time estimation, lower positive affect, lower extraversion, and higher verbal memory. In total, the model accounted for 38% of the variability in interoceptive sensitivity (R2 = .38). These results suggest that, among older adults, interoceptive sensitivity is facilitative for aspects of cognition but perhaps disruptive for certain aspects of emotional experience.

Using Postmeal Measures and Manipulations to Investigate Hippocampal Mnemonic Control of Eating Behavior

Episodic meal-related memories provide the brain with a powerful mechanism for tracking and controlling eating behavior because they contain a detailed record of recent energy intake that likely outlasts the physiological signals generated by feeding bouts. This review briefly summarizes evidence from human participants showing that episodic meal-related memory limits later eating behavior and then describes our research aimed at investigating whether hippocampal neurons mediate the inhibitory effects of meal-related memory on subsequent feeding. Our approach has been inspired by pioneering work conducted by Ivan Izquierdo and others who used posttraining manipulations to investigate memory consolidation. This review describes the rationale and value of posttraining manipulations, how Izquierdo used them to demonstrate that dorsal hippocampal (dHC) neurons are critical for memory consolidation, and how we have adapted this strategy to investigate whether dHC neurons are necessary for mnemonic control of energy intake. I describe our evidence showing that ingestion activates the molecular processes necessary for synaptic plasticity and memory during the early postprandial period, when the memory of the meal would be undergoing consolidation, and then summarize our findings showing that neural activity in dHC neurons is critical during the early postprandial period for limiting future intake. Collectively, our evidence supports the hypothesis that dHC neurons mediate the inhibitory effects of ingestion-related memory on future intake and demonstrates that post-experience memory modulation is not confined to artificial laboratory memory tasks.

An insula-based network mediates the relation between rumination and interoceptive sensibility in the healthy population

BACKGROUND

Individuals sometimes continuously centered their attention on the same thoughts. When such process tends to be negative and self-referential, we delineated this mental state as rumination, which may undermine body's perception of endogenous signal, but little is known about the certainly relationship and the potential neural mechanisms.

METHODS

Rumination and interoceptive sensibility were measured by questionnaires, then insula-related network of rumination dimensions were examined by the whole brain resting-state functional connectivity (FC) in 479 college students, and whether the insula-based network mediate the relationship between rumination and interoceptive sensibility were tested.

RESULTS

Rumination (including brooding reflective pondering) and interoceptive sensibility showed positive correlations. The neural mechanisms of brooding and reflective pondering were all related to the insula-networks, to be specific, brooding was positively correlated with the FC between the left posterior insula (PI) and left parahippocampal gyrus/ hippocampus (PHG), reflective pondering were positively correlated with the FC between the insula subregion and the dorsolateral prefrontal cortex. Moreover, the relationship between brooding and interoceptive sensibility was mediated by the FC between left PI and left PHG.

LIMITATIONS

We just tested the relationship between rumination and interoceptive sensibility at a cross-sectional level, but it is unclear that whether the longitudinal relationship would be predicted by the related network.

CONCLUSIONS

Our findings provided new insights into neural mechanisms of brooding and reflective pondering, also the integration of brooding and interoceptive sensibility. The insula-related networks may contribute crucially to rumination and interoception.

Emotional representations of space vary as a function of peoples' affect and interoceptive sensibility

Most research on people's representation of space has focused on spatial appraisal and navigation. But there is more to space besides navigation and assessment: people have different emotional experiences at different places, which create emotionally tinged representations of space. Little is known about the emotional representation of space and the factors that shape it. The purpose of this study was to develop a graphic methodology to study the emotional representation of space and some of the environmental features (non-natural vs. natural) and personal features (affective state and interoceptive sensibility) that modulate it. We gave participants blank maps of the region where they lived and asked them to apply shade where they had happy/sad memories, and where they wanted to go after Covid-19 lockdown. Participants also completed self-reports on affective state and interoceptive sensibility. By adapting methods for analyzing neuroimaging data, we examined shaded pixels to quantify where and how strong emotions are represented in space. The results revealed that happy memories were consistently associated with similar spatial locations. Yet, this mapping response varied as a function of participants' affective state and interoceptive sensibility. Certain regions were associated with happier memories in participants whose affective state was more positive and interoceptive sensibility was higher. The maps of happy memories, desired locations to visit after lockdown, and regions where participants recalled happier memories as a function of positive affect and interoceptive sensibility overlayed significantly with natural environments. These results suggest that people's emotional representations of their environment are shaped by the naturalness of places, and by their affective state and interoceptive sensibility.

Altered hippocampal microstructure and function in children who experienced Hurricane Irma

Hurricane Irma was the most powerful Atlantic hurricane in recorded history, displacing 6 million and killing over 120 people in the state of Florida alone. Unpredictable disasters like Irma are associated with poor cognitive and health outcomes that can disproportionately impact children. This study examined the effects of Hurricane Irma on the hippocampus and memory processes previously related to unpredictable stress. We used an innovative application of an advanced diffusion-weighted imaging technique, restriction spectrum imaging (RSI), to characterize hippocampal microstructure (i.e., cell density) in 9- to 10-year-old children who were exposed to Hurricane Irma relative to a non-exposed control group (i.e., assessed the year before Hurricane Irma). We tested the hypotheses that the experience of Hurricane Irma would be associated with decreases in: (a) hippocampal cellularity (e.g., neurogenesis), based on known associations between unpredictable stress and hippocampal alterations; and (b) hippocampal-related memory function as indexed by delayed recall. We show an association between decreased hippocampal cellularity and delayed recall memory in children who experienced Hurricane Irma relative to those who did not. These findings suggest an important role of RSI for assessing subtle microstructural changes related to functionally significant changes in the developing brain in response to environmental events.

The congruence of interoceptive predictions and hippocampal-related memory

Interoceptive deficits are associated with medial temporal lobe (MTL) lesions, and especially the hippocampus, which may relate to interoception's reliance upon predictive coding and hence on mnemonic processes. Here, we develop a new task to assess interoceptive predictions and assess their dependence upon MTL memory systems. Healthy participants were asked to imagine and predict what they would feel like across nine interoceptive situations. Later, each situation was physically experienced, and participants reported what they actually felt. An index of predictive congruence was derived and correlated with a neuropsychological measure of hippocampal dependent learning and memory (HDLM), finding that more accurate predictions were associated with better HDLM (Cohen's d = 0.5). We suggest the MTL, and in particular the hippocampus, generates contextually appropriate episodic memories, providing a predictive framework for interpreting afferent bodily neurohormonal signals. The loss of this capacity may account for the profound interoceptive deficits observed following MTL lesions.

An Active Inference Approach to Interoceptive Psychopathology

Interoception refers to the process by which the nervous system senses and integrates signals originating from within the body, providing a momentary mapping of the body's internal landscape and its relationship to the outside world. Active inference is based on the premise that afferent sensory input to the brain is constantly shaped and modified by prior expectations. In this review we propose that interoceptive psychopathology results from two primary interoceptive dysfunctions: First, individuals have abnormally strong expectations of the situations that elicit bodily change (i.e., hyperprecise priors), and second, they have great difficulty adjusting these expectations when the environment changes (i.e., context rigidity). Here we discuss how these dysfunctions potentially manifest in mental illness and how interventions aimed at altering interoceptive processing can help the brain create a more realistic model of its internal state.

Interoceptive accuracy and its impact on neuronal responses to olfactory stimulation in the insular cortex

The insular cortex plays a key role in the integration of multimodal information and in interoceptive and exteroceptive processing. For instance, neurons in the central dorsal insula that are active during interoceptive tasks, also show an adaptation to gustatory stimulation. We tested the link between interoception and exteroception for the olfactory system (i.e., the second domain of chemosensation). In a sample of 31 participants, olfactory function was assessed in a two dimensional approach while the Heartbeat Perception Task served as a measurement for cardiac interoceptive accuracy. Subsequent fMRI sessions were performed on a 3‐Tesla MR scanner containing 12–15 olfactory stimulation trials with a mildly pleasant food‐related odor (coffee). Persons scoring high in the cardiac interoceptive accuracy task presented stronger smelling abilities as well as enhanced BOLD responses following olfactory stimulation. The olfactory stimulation triggered enhanced insular activation patterns in the central dorsal insular cortex. Consistent with prior findings on the coherence of gustatory and interoceptive processing in the central dorsal insula, these results base the insula as a common region for the integration of interoception and exteroception. We propose an explanatory model of how exteroception triggers the integration of intero‐ and exteroceptive sensations in the central dorsal insular cortex.

Disentangling the Contribution of Spatial Reference Frames to Executive Functioning in Healthy and Pathological Aging: An Experimental Study with Virtual Reality

A growing body of evidence pointed out that a decline in effectively using spatial reference frames for categorizing information occurs both in normal and pathological aging. Moreover, it is also known that executive deficits primarily characterize the cognitive profile of older individuals. Acknowledging this literature, the current study was aimed to specifically disentangle the contribution of the cognitive abilities related to the use of spatial reference frames to executive functioning in both healthy and pathological aging. 48 healthy elderly individuals and 52 elderly suffering from probable Alzheimer’s Disease (AD) took part in the study. We exploited the potentiality of Virtual Reality to specifically measure the abilities in retrieving and syncing between different spatial reference frames, and then we administrated different neuropsychological tests for evaluating executive functions. Our results indicated that allocentric functions contributed significantly to the planning abilities, while syncing abilities influenced the attentional ones. The findings were discussed in terms of previous literature exploring relationships between cognitive deficits in the first phase of AD.