The contribution of short-term memory for sound features to speech-in-noise perception and cognition.

Speech-in-noise (SIN) perception is a fundamental ability that declines with aging, as does general cognition. We assess whether auditory cognitive ability, in particular short-term memory for sound features, contributes to both. We examined how auditory memory for fundamental sound features, the carrier frequency and amplitude modulation rate of modulated white noise, contributes to SIN perception. We assessed SIN in 153 healthy participants with varying degrees of hearing loss using measures that require single-digit perception (the Digits-in-Noise, DIN) and sentence perception (Speech-in-Babble, SIB). Independent variables were auditory memory and a range of other factors including the Pure Tone Audiogram (PTA), a measure of dichotic pitch-in-noise perception (Huggins pitch), and demographic variables including age and sex. Multiple linear regression models were compared using Bayesian Model Comparison. The best predictor model for DIN included PTA and Huggins pitch (r2 = 0.32, p < 0.001), whereas the model for SIB included the addition of auditory memory for sound features (r2 = 0.24, p < 0.001). Further analysis demonstrated that auditory memory also explained a significant portion of the variance (28 %) in scores for a screening cognitive test for dementia. Auditory memory for non-speech sounds may therefore provide an important predictor of both SIN and cognitive ability.

Subjective hearing loss is not associated with an increased risk of Alzheimer's disease dementia.

Hearing loss is a risk-factor for dementia but the reasons for this are unclear. Subjective hearing loss is related to increased future dementia risk, however, this metric has not been previously examined with cognitive, neuroimaging and biochemical measures that are relevant to Alzheimer's disease. We assessed Cognitively Normal and Mild Cognitively Impaired participants from the Alzheimer's Disease Neuroimaging Initiative with subjective hearing loss to examine if they had faster decline in episodic memory scores, hippocampal volume and greater pTau positivity. The likelihood of a dementia diagnosis in hearing impaired participants over a 5-year period was also assessed. There were no statistically significant differences between the hearing subgroups over a 5-year period nor were there in conversions to a dementia diagnosis. Objective hearing loss metrics may provide a more reliable link between hearing loss and dementia risk.

Sensory Loss and Risk of Dementia.

Sensory loss in olfaction, vision, and hearing is a risk factor for dementia, but the reasons for this are unclear. This review presents the neurobiological evidence linking each sensory modality to specific dementias and explores the potential mechanisms underlying this. Olfactory deficits can be linked to direct neuropathologic changes in the olfactory system due to Alzheimer disease and Parkinson disease, and may be a marker of disease severity. Visual deficits potentially increase dementia risk in a vulnerable individual by reducing resilience to dementia. Hearing deficits may indicate a susceptibility to Alzheimer disease through a variety of mechanisms. More generally, sensory impairment could be related to factors associated with resilience against dementia. Further research is needed to tease out the specific and synergistic effects of sensory impairment. Studying sensory loss in relation to neurodegenerative biomarkers is necessary to clarify the mechanisms involved. This could produce new monitoring and management strategies for people at risk of dementia.

The hearing hippocampus.

The hippocampus has a well-established role in spatial and episodic memory but a broader function has been proposed including aspects of perception and relational processing. Neural bases of sound analysis have been described in the pathway to auditory cortex, but wider networks supporting auditory cognition are still being established. We review what is known about the role of the hippocampus in processing auditory information, and how the hippocampus itself is shaped by sound. In examining imaging, recording, and lesion studies in species from rodents to humans, we uncover a hierarchy of hippocampal responses to sound including during passive exposure, active listening, and the learning of associations between sounds and other stimuli. We describe how the hippocampus' connectivity and computational architecture allow it to track and manipulate auditory information - whether in the form of speech, music, or environmental, emotional, or phantom sounds. Functional and structural correlates of auditory experience are also identified. The extent of auditory-hippocampal interactions is consistent with the view that the hippocampus makes broad contributions to perception and cognition, beyond spatial and episodic memory. More deeply understanding these interactions may unlock applications including entraining hippocampal rhythms to support cognition, and intervening in links between hearing loss and dementia.

A specific relationship between musical sophistication and auditory working memory.

Previous studies have found conflicting results between individual measures related to music and fundamental aspects of auditory perception and cognition. The results have been difficult to compare because of different musical measures being used and lack of uniformity in the auditory perceptual and cognitive measures. In this study we used a general construct of musicianship, musical sophistication, that can be applied to populations with widely different backgrounds. We investigated the relationship between musical sophistication and measures of perception and working memory for sound by using a task suitable to measure both. We related scores from the Goldsmiths Musical Sophistication Index to performance on tests of perception and working memory for two acoustic features-frequency and amplitude modulation. The data show that musical sophistication scores are best related to working memory for frequency in an analysis that accounts for age and non-verbal intelligence. Musical sophistication was not significantly associated with working memory for amplitude modulation rate or with the perception of either acoustic feature. The work supports a specific association between musical sophistication and working memory for sound frequency.

The Motor Basis for Misophonia.

Misophonia is a common disorder characterized by the experience of strong negative emotions of anger and anxiety in response to certain everyday sounds, such as those generated by other people eating, drinking, and breathing. The commonplace nature of these "trigger" sounds makes misophonia a devastating disorder for sufferers and their families. How such innocuous sounds trigger this response is unknown. Since most trigger sounds are generated by orofacial movements (e.g., chewing) in others, we hypothesized that the mirror neuron system related to orofacial movements could underlie misophonia. We analyzed resting state fMRI (rs-fMRI) connectivity (N = 33, 16 females) and sound-evoked fMRI responses (N = 42, 29 females) in misophonia sufferers and controls. We demonstrate that, compared with controls, the misophonia group show no difference in auditory cortex responses to trigger sounds, but do show: (1) stronger rs-fMRI connectivity between both auditory and visual cortex and the ventral premotor cortex responsible for orofacial movements; (2) stronger functional connectivity between the auditory cortex and orofacial motor area during sound perception in general; and (3) stronger activation of the orofacial motor area, specifically, in response to trigger sounds. Our results support a model of misophonia based on "hyper-mirroring" of the orofacial actions of others with sounds being the "medium" via which action of others is excessively mirrored. Misophonia is therefore not an abreaction to sounds, per se, but a manifestation of activity in parts of the motor system involved in producing those sounds. This new framework to understand misophonia can explain behavioral and emotional responses and has important consequences for devising effective therapies.SIGNIFICANCE STATEMENT Conventionally, misophonia, literally "hatred of sounds" has been considered as a disorder of sound emotion processing, in which "simple" eating and chewing sounds produced by others cause negative emotional responses. Our data provide an alternative but complementary perspective on misophonia that emphasizes the action of the trigger-person rather than the sounds which are a byproduct of that action. Sounds, in this new perspective, are only a "medium" via which action of the triggering-person is mirrored onto the listener. This change in perspective has important consequences for devising therapies and treatment methods for misophonia. It suggests that, instead of focusing on sounds, which many existing therapies do, effective therapies should target the brain representation of movement.

How Can Hearing Loss Cause Dementia?

Epidemiological studies identify midlife hearing loss as an independent risk factor for dementia, estimated to account for 9% of cases. We evaluate candidate brain bases for this relationship. These bases include a common pathology affecting the ascending auditory pathway and multimodal cortex, depletion of cognitive reserve due to an impoverished listening environment, and the occupation of cognitive resources when listening in difficult conditions. We also put forward an alternate mechanism, drawing on new insights into the role of the medial temporal lobe in auditory cognition. In particular, we consider how aberrant activity in the service of auditory pattern analysis, working memory, and object processing may interact with dementia pathology in people with hearing loss. We highlight how the effect of hearing interventions on dementia depends on the specific mechanism and suggest avenues for work at the molecular, neuronal, and systems levels to pin this down.

Speech-in-noise detection is related to auditory working memory precision for frequency.

Speech-in-noise (SiN) perception is a critical aspect of natural listening, deficits in which are a major contributor to the hearing handicap in cochlear hearing loss. Studies suggest that SiN perception correlates with cognitive skills, particularly phonological working memory: the ability to hold and manipulate phonemes or words in mind. We consider here the idea that SiN perception is linked to a more general ability to hold sound objects in mind, auditory working memory, irrespective of whether the objects are speech sounds. This process might help combine foreground elements, like speech, over seconds to aid their separation from the background of an auditory scene. We investigated the relationship between auditory working memory precision and SiN thresholds in listeners with normal hearing. We used a novel paradigm that tests auditory working memory for non-speech sounds that vary in frequency and amplitude modulation (AM) rate. The paradigm yields measures of precision in frequency and AM domains, based on the distribution of participants' estimates of the target. Across participants, frequency precision correlated significantly with SiN thresholds. Frequency precision also correlated with the number of years of musical training. Measures of phonological working memory did not correlate with SiN detection ability. Our results demonstrate a specific relationship between working memory for frequency and SiN. We suggest that working memory for frequency facilitates the identification and tracking of foreground objects like speech during natural listening. Working memory performance for frequency also correlated with years of musical instrument experience suggesting that the former is potentially modifiable.

Characterizing memory loss in patients with autoimmune limbic encephalitis hippocampal lesions.

Since the publication of Scoville and Milner's (1957) seminal paper, the precise functional role played by the hippocampus in support of human memory has been fiercely debated. For instance, the single question of whether the hippocampus plays a time-limited or an indelible role in the recollection of personal memories led to a deep and tenacious schism within the field. Similar polarizations arose between those who debated the precise nature of the role played by the hippocampus in support of semantic relative to episodic memories and in recall/recollection relative to familiarity-based recognition. At the epicenter of these divisions lies conflicting neuropsychological findings. These differences likely arise due to the consistent use of heterogeneous patient populations to adjudicate between these positions. Here we utilized traditional neuropsychological measures in a homogenous patient population with a highly discrete hippocampal lesion (i.e., VGKCC-Ab related autoimmune limbic encephalitis patients). We observed consistent impairment of recent episodic memories, a present but less striking impairment of remote episodic memories, preservation of personal semantic memory, and recall but not recognition memory deficits. We conclude that this increasingly well-characterized patient group may represent an important homogeneous population in which the functional role played by the hippocampus may be more precisely delineated.

Niemann-Pick type C: contemporary diagnosis and treatment of a classical disorder.

Niemann-Pick type C is an uncommon neurodegenerative lysosomal storage disorder that can cause a progressive neuropsychiatric syndrome associated with supranuclear vertical gaze palsy and a movement disorder. There have been recent developments in testing that make diagnosis easier and new therapies that aim to stabilise the disease process. A new biochemical test to measure serum cholesterol metabolites supersedes the skin biopsy and is practical and robust. It is treatable with miglustat, a drug that inhibits glycosphingolipid synthesis. We describe a patient, aged 22 years, with juvenile-onset Niemann-Pick type C who presented with seizures and a label of 'cerebral palsy'. We describe the approach to this syndrome in general, and highlight the classical features and red flags that should alert a neurologist to this treatable condition.

Urinary, bowel and sexual symptoms in a cohort of patients with Friedreich's ataxia.

BACKGROUND: Pelvic symptoms are distressing symptoms experienced by patients with Friedreich's Ataxia (FRDA). The aim of this study was to describe the prevalence of lower urinary tract symptoms (LUTS), bowel and sexual symptoms in FRDA. METHODS: Questionnaire scores measuring LUTS, bowel and sexual symptoms were analysed with descriptive statistics as a cohort and as subgroups (Early/Late-onset and Early/Late-stage FRDA) They were also correlated with validated measures of disease severity including those of ataxia severity, non-ataxic symptoms and activities of daily living. RESULTS: 80% (n = 46/56) of patients reported LUTS, 64% (n = 38/59) reported bowel symptoms and 83% (n = 30/36) reported sexual symptoms. Urinary and bowel or sexual symptoms were significantly likely to co-exist among patients. Late-onset FRDA patients were also more likely to report LUTS than early-onset ones. Patients with a longer disease duration reported higher LUTS scores and poorer quality of life scores related to urinary symptoms. CONCLUSIONS: A high proportion of FRDA have symptoms suggestive of LUTS, bowel and sexual dysfunction. This is more marked with greater disease duration and later disease onset. These symptoms need to be addressed by clinicians as they can have a detrimental effect on patients.

A surprising diagnosis: metastatic prostate cancer causing cervical lymphadenopathy.

Cervical lymphadenopathy as an initial presentation for metastatic prostate cancer has been rarely described. Less than 30 cases have been published in medical literature whereby a lymph node biopsy revealed immunoreactivity for prostate-specific antigen (PSA) diagnosing metastatic prostate cancer. We present a unique scenario whereby an asymptomatic patient with previous high-risk gastric cancer presented to clinic with cervical lymphadenopathy. A hunt for a recurrence ensued to no avail and imaging of the head and neck showed no hint of a primary malignancy in those regions. A lymph node biopsy was undertaken which showed elements suggesting metastatic prostate cancer. The patient developed symptoms of urinary outflow obstruction shortly afterwards. Blood tests revealed a very high PSA and a bone scan showed widespread bony metastasis. He was started on androgen deprivation therapy with an improvement of his PSA and symptoms. A regular clinic follow-up has shown stable disease.

Occult bladder injury after laparoscopic appendicectomy.

Minimally invasive procedures have revolutionised surgery by reducing pain and the length of hospital stay for patients. These are not simple procedures and training in laparoscopic surgery is an arduous process. Meticulous preparation prior to surgery is paramount to prevent complications. We report a rare complication involving a 35-year-old patient who underwent a laparoscopic appendicectomy for a perforated appendix. Two days after surgery the patient experienced redness and swelling in the lower abdominal region and oliguria. A delayed computer tomography (CT) scan revealed contrast leakage around the bladder spreading within the peritoneal cavity consistent with an intraperitoneal bladder perforation. She underwent urinary catheterisation for 6 days. A follow-up CT cystogram showed no evidence of leakage into the peritoneal cavity. This case highlights the need for thorough preparation prior to laparoscopic surgery and careful manipulation of instruments during routine procedures to minimise the risk of serious patient complications such as the aforementioned.