Haptic recognition memory and lateralisation for verbal and nonverbal shapes

Laterality effects generally refer to an advantage for verbal processing in the left hemisphere and for non-verbal processing in the right hemisphere, and are often demonstrated in memory tasks in vision and audition. In contrast, their role in haptic memory is less understood. In this study, we examined haptic recognition memory and laterality for letters and nonsense shapes. We used both upper and lower case letters, with the latter designed as more complex in shape. Participants performed a recognition memory task with the left and right hand separately. Recognition memory performance (capacity and bias-free d') was higher and response times were faster for upper case letters than for lower case letters and nonsense shapes. The right hand performed best for upper case letters when it performed the task after the left hand. This right hand/left hemisphere advantage appeared for upper case letters, but not lower case letters, which also had a lower memory capacity, probably due to their more complex spatial shape. These findings suggest that verbal laterality effects in haptic memory are not very prominent, which may be due to the haptic verbal stimuli being processed mainly as spatial objects without reaching robust verbal coding into memory.Peer reviewe

Self-Conscious Affect Is Modulated by Rapid Eye Movement Sleep but Not by Targeted Memory Reactivation–A Pilot Study

The neurophysiological properties of rapid eye movement sleep (REMS) are believed to tune down stressor-related emotional responses. While prior experimental findings are controversial, evidence suggests that affective habituation is hindered if REMS is fragmented. To elucidate the topic, we evoked self-conscious negative affect in the participants (N = 32) by exposing them to their own out-of-tune singing in the evening. Affective response to the stressor was measured with skin conductance response and subjectively reported embarrassment. To address possible inter-individual variance toward the stressor, we measured the shame-proneness of participants with an established questionnaire. The stressor was paired with a sound cue to pilot a targeted memory reactivation (TMR) protocol during the subsequent night's sleep. The sample was divided into three conditions: control (no TMR), TMR during slow-wave sleep, and TMR during REMS. We found that pre- to post-sleep change in affective response was not influenced by TMR. However, REMS percentage was associated negatively with overnight skin conductance response habituation, especially in those individuals whose REMS was fragmented. Moreover, shame-proneness interacted with REM fragmentation such that the higher the shame-proneness, the more the affective habituation was dependent on non-fragmented REMS. In summary, the potential of REMS in affective processing may depend on the quality of REMS as well as on individual vulnerability toward the stressor type.Peer reviewe

Endogenous circadian temperature rhythms relate to adolescents' daytime physical activity

Circadian rhythms relate to multiple aspects of health and wellbeing, including physical activity patterns. Susceptible circadian regulation predisposes to circadian misalignment, poor sleep, sleep deprivation, increased sleepiness, and thereby sedentary behavior. Adolescents' circadian regulation is particularly vulnerable, and may lead to sedentary behavior. To investigate which factors associate strongest between physical activity (PA) and circadian behavior, we conducted multimodal circadian rhythm analyses. We investigate how individual characteristics of habitual circadian patterns associate with objectively measured PA. We studied 312 adolescents [70% females) (56% with delayed sleep phase (DSP)], mean age 16.9 years. Circadian period length, temperature mesor (estimated 24 h midline) and amplitude (difference between mesor and peak) were measured using distally attached thermologgers (ibutton 1922L, 3-day-measurement). We additionally utilized algorithm-formed clusters of circadian rhythmicity. Sleep duration, timing, DSP, and PA were measured using actigraphs (GeneActiv Original, 10-day-measurement). We found that continuous circadian period length was not associated with PA, but lower mesor and higher amplitude were consistently associated with higher levels of PA as indicated by mean Metabolic Equivalent (METmean) and moderate-to-vigorous PA (MVPA), even when controlling for sleep duration. Separate circadian clusters formed by an algorithm also reflected distinct patterns of PA accordingly. Late sleepers and those with DSP were less likely to engage in MVPA compared to non-DSP and had more sedentary behavior. Adolescents who engage in higher levels or high-intensity PA have better circadian regulation, as measured by different objective methods including distal temperature measurements as well as actigraphy-measured sleep-wake behavior.Peer reviewe

Imaging Real-Time Tactile Interaction With Two-Person Dual-Coil fMRI

Studies of brain mechanisms supporting social interaction are demanding because real interaction only occurs when persons are in contact. Instead, most brain imaging studies scan subjects individually. Here we present a proof-of-concept demonstration of two-person blood oxygenation dependent (BOLD) imaging of brain activity from two individuals interacting inside the bore of a single MRI scanner. We developed a custom 16-channel (8 + 8 channels) two-helmet coil with two separate receiver-coil pairs providing whole-brain coverage, while bringing participants into a shared physical space and realistic face-to-face contact. Ten subject pairs were scanned with the setup. During the experiment, subjects took turns in tapping each other's lip versus observing and feeling the taps timed by auditory instructions. Networks of sensorimotor brain areas were engaged alternatingly in the subjects during executing motor actions as well as observing and feeling them; these responses were clearly distinguishable from the auditory responses occurring similarly in both participants. Even though the signal-to-noise ratio of our coil system was compromised compared with standard 32-channel head coils, our results show that the two-person fMRI scanning is feasible for studying the brain basis of social interaction

Inter-Subject Synchronization of Prefrontal Cortex Hemodynamic Activity During Natural Viewing

Hemodynamic activity in occipital, temporal, and parietal cortical areas were recently shown to correlate across subjects during viewing of a 30-minute movie clip. However, most of the frontal cortex lacked between-subject correlations. Here we presented 12 healthy naïve volunteers with the first 72 minutes of a movie (“Crash”, 2005, Lions Gate Films) outside of the fMRI scanner to involve the subjects in the plot of the movie, followed by presentation of the last 36 minutes during fMRI scanning. We observed significant between-subjects correlation of fMRI activity in especially right hemisphere frontal cortical areas, in addition to the correlation of activity in temporal, occipital, and parietal areas. It is possible that this resulted from the subjects following the plot of the movie and being emotionally engaged in the movie during fMRI scanning. We further show that probabilistic independent component analysis (ICA) reveals meaningful activations in individual subjects during natural viewing

Differential effects of ageing on the neural processing of speech and singing production

BackgroundUnderstanding healthy brain ageing has become vital as populations are ageing rapidly and age-related brain diseases are becoming more common. In normal brain ageing, speech processing undergoes functional reorganisation involving reductions of hemispheric asymmetry and overactivation in the prefrontal regions. However, little is known about how these changes generalise to other vocal production, such as singing, and how they are affected by associated cognitive demands.MethodsThe present cross-sectional fMRI study systematically maps the neural correlates of vocal production across adulthood (N=100, age 21–88 years) using a balanced 2x3 design where tasks varied in modality (speech: proverbs / singing: song phrases) and cognitive demand (repetition / completion from memory / improvisation).ResultsIn speech production, ageing was associated with decreased left pre- and postcentral activation across tasks and increased bilateral angular and right inferior temporal and fusiform activation in the improvisation task. In singing production, ageing was associated with increased activation in medial and bilateral prefrontal and parietal regions in the completion task, whereas other tasks showed no ageing effects. Direct comparisons between the modalities showed larger age-related activation changes in speech than singing across tasks, including a larger left-to-right shift in lateral prefrontal regions in the improvisation task.ConclusionThe present results suggest that the brains’ singing network undergoes differential functional reorganisation in normal ageing compared to the speech network, particularly during a task with high executive demand. These findings are relevant for understanding the effects of ageing on vocal production as well as how singing can support communication in healthy ageing and neurological rehabilitation

Selective Attention Increases Both Gain and Feature Selectivity of the Human Auditory Cortex

Background. An experienced car mechanic can often deduce what’s wrong with a car by carefully listening to the sound of the ailing engine, despite the presence of multiple sources of noise. Indeed, the ability to select task-relevant sounds for awareness, whilst ignoring irrelevant ones, constitutes one of the most fundamental of human faculties, but the underlying neural mechanisms have remained elusive. While most of the literature explains the neural basis of selective attention by means of an increase in neural gain, a number of papers propose enhancement in neural selectivity as an alternative or a complementary mechanism. Methodology/Principal Findings. Here, to address the question whether pure gain increase alone can explain auditory selective attention in humans, we quantified the auditory cortex frequency selectivity in 20 healthy subjects by masking 1000-Hz tones by continuous noise masker with parametrically varying frequency notches around the tone frequency (i.e., a notched-noise masker). The task of the subjects was, in different conditions, to selectively attend to either occasionally occurring slight increments in tone frequency (1020 Hz), tones of slightly longer duration, or ignore the sounds. In line with previous studies, in the ignore condition, the global field power (GFP) of event-related brain responses at 100 ms from the stimulus onset to the 1000-Hz tones was suppressed as a function of the narrowing of the notch width. During the selective attention conditions, the suppressant effect of the noise notch width on GFP was decreased, but as a function significantly different from a multiplicative one expected on the basis of simple gain model of selective attention. Conclusions/Significance. Our results suggest that auditory selective attention in humans cannot be explained by a gai

Tarkkaavaisuuden vaikutus hermosolujen ärsykepiirreviritykseen

Tarkkaavaisuuden avulla valikoimme kulloisellakin hetkellä tärkeimmät ärsykkeet. Tässä kokeessa tutkittiin tarkkaavaisuuden vaikutuksia ihmisen kuuloaivokuorella käyttäen sekä elektroenkefalografiaa (EEG) että magnetoenkefalografiaa (MEG) tutkimusmenetelminä. Tutkimusoletuksenamme oli, että tarkkaavaisuus terävöittää hermosolujen reaktioiden viritystä ärsykkeen tarkkailtavien piirteiden osalta. Työn yhteydessä tehtiin psykofyysinen koe käyttäen ääniärsykkeitä ja mitaten samalla joko EEG:tä tai MEG:tä. Kokeessa esitettiin 1000 Hz siniääniä jatkuvan kohinapeiton kanssa. Kohina luotiin kaistanestosuodattamalla valkoista kohinaa vaihtelevilla suotimen leveyksillä (+-500...0) 1000 Hz ympäriltä. Suodatettu kaista pidettiin vakiona kunkin herätepotentiaalin ja herätekentän nauhoituksen ajan. Kokeessa oli kolme tilannetta: kaksi tarkkaavaisuutta vaativaa tehtävää, jossa koehenkilön piti kiinnittää huomiota joko äänen korkeuseroon tai äänen keston eroon, sekä yksi passiivinen tilanne, jossa koehenkilö katsoi hiljaista animaatiofilmiä siten, että kokeessa käytetyt äänet kuuluivat taustalla. Kokeen tulokset osoittivat, että tarkkaavaisuus muuttaa hermosolujen vasteiden suuruutta. Ääniärsykkeen herätepotentiaalin komponentit (P50, Nl00 ja P200) muuttuivat siten, että erityisesti N 100:n amplitudi oli suurempi tarkkaavaisuutta vaativissa tilanteissa kuin passiivisessa tilanteessa. Tämä tapahtui kuitenkin vain muutamilla kapeimmilla kaistanestosuotimen leveyksillä. Tämä viittaisi siihen, että vaikutus ei ole ainoastaan hermosolujen aktivaatiota ja herätepotentiaalin komponenttien amplitudeja kautta linjan lisäävä, vaan että tarkkaavaisuustilanteessa N100-komponentin synnyttäneet hermosolut ovat myös tarkemmin virittyneet tarkkaillun äänen taajuudelle. Tuloksia voi hyödyntää esimerkiksi tarkkaavaisuushäiriöiden, kuten Alzheimerin taudin, skitsofrenian tai ADHD-oireyhtymän kliinisissä tutkimuksissa tai taudinmäärityksessä. Suuntaa-antavia tuloksia tarkkaavaisuushäiriön suuruudesta voidaan saada siten, että käytetään sopivia ääniärsykkeitä, ja ärsykkeisiin liittyviä hermosolujen vasteita verrataan terveiltä ihmisiltä saatuihin vasteisiin

Mittauksia ja malleja ihmisen kuuloaivokuoren top-down -vaikutuksista

Our senses rapidly adapt to the sensory information and task requirements. These short-term, plastic changes especially in the central nervous system are necessary for goal-directed and active behavior. Nevertheless, partly due to methodological limitations, the neural mechanisms underlying improved perception during selective attention are not well understood. For instance, human auditory cortex activity is enhanced while engaging in an auditory task, but whether such enhancement involves a larger-extend or a more specific response from a sharply tuned neuronal population remains vague. In addition to unimodal attention effects, our senses can influence each others' processing. Seeing a person articulate can both enhance and modify the perception of acoustic speech and even induce activation in the auditory areas. The goal of the Thesis was to study the neural basis of these auditory cortex modulations both due to selective attention and cross-modal interactions while lipreading. This Thesis consists of a series of four studies where the brain activity was recorded with electroencephalography (EEG) and its magnetic counterpart, magnetoencephalography (MEG). The results show that 1) evoked responses mainly from the secondary auditory areas were rapidly enhanced by a feature-specific manner during a discrimination task, where bottom-up and top-down processing were modified by stimulus and task design, 2) lipreading task suppressed auditory-cortex responses both generally and specifically in the case when sound was related to the articulatory gestures, and 3) lipreading and covert speech production tasks dynamically suppressed auditory cortex reactivity, possibly via an efference copy signal from the speech-production system. Together, these studies expand the knowledge on how the human auditory cortex function is modulated under top-down influence. The modulations due to selective attention and cross-modal interactions while lipreading are opposite at the level of evoked responses: selective attention enhances and lipreading suppresses the responses, but both effects can be feature-selective. The results show that the auditory system is highly dependent on the current task requirements, showing adaptive and goal-dependent functioning.Ihmisen aistit mukautuvat nopeasti havaintoinformaation ja tilanteen vaatimusten mukaan. Nämä lyhytaikaiset, plastiset muutokset erityisesti keskushermoston tasolla ovat välttämättömiä tehokkaalle toiminnalle. Tarkkaavaisuustilanteissa todetun parantuneen havaintokyvyn hermostollista perustaa ei kuitenkaan täysin tunneta, osin rajoitettujen tutkimusmenetelmien takia. Esimerkiksi ihmisen kuuloaivokuoren toiminta tehostuu ääneen liittyvää tehtävää tehdessä, mutta on epäselvää liittyykö tähän tehostumiseen hermosolujen laajempialaiset vai tarkemmin virittyneet aktivaatiot. Yhteen aistiin liittyvien tehostumismekanismien lisäksi aistit vaikuttavat toinen toistensa toimintaan. Toisen puhujan huulten liikkeiden näkeminen aktivoi kuuloaivokuorta, sen lisäksi huuliltaluku sekä helpottaa puheen ymmärtämistä että tietyissä tilanteissa muuttaa havaintoa. Tämän väitöskirjatyön tavoitteena oli tutkia valikoivan tarkkaavaisuuden ja huuliltaluvun aikaisen aistienvälisen vuorovaikutuksen hermostollista perustaa terveiden ihmisten kuuloaivokuorella. Väitöskirjatyö koostuu neljästä osatutkimuksesta, joissa aivojen aktivaatioiden aiheuttamia sähkömagneettisia signaaleja tutkittiin käyttämällä tutkimusmenetelminä sekä elektroenkefalografiaa (EEG) että magnetoenkefalografiaa (MEG). Tulokset osoittivat, että 1) pääosin sekundaarisella kuuloaivokuorella syntyvät herätevasteet muovautuivat piirreriippuvaisesti sellaisen äänien erottelutehtävän aikana, jossa bottom-up ja top-down -prosessointia muokattiin monimutkaisilla ääniärsykkeillä ja ohjeistuksella, 2) huuliltaluku vaimensi kuuloaivokuorella syntyneitä vasteita sekä yleisesti että piirreriippuvaisesti mikäli ääni liittyi nähtyyn artikulaatioon, 3) huuliltaluku ja hiljainen puheentuotto vaimensivat dynaamisesti kuuloaivokuoren vasteita, mahdollisesti puheentuottojärjestelmästä lähteneen efferentin hermovasteen takia. Tämän väitöskirjan tulokset laajentavat tietämystä siitä, miten top-down -vaikutukset näkyvät ihmisen kuuloaivokuorella. Tulosten perusteella voidaan sanoa, että kuuloaivokuoren toiminnassa näkyy valikoivan tarkkaavaisuuden ja huuliltalukutehtävän aikana suunnaltaan päinvastaisia muutoksia verrokkitilanteeseen nähden: tarkkaavaisuus suurentaa ja huuliltaluku vaimentaa vasteita siten, että molemmat vaikutukset ovat riippuvaisia käytetyistä ärsykkeistä. Tämä osoittaa, että ihmisen kuulojärjestelmän toiminta muovautuu nopeasti tehtävän vaatimusten mukaan