Inferring common cognitive mechanisms from brain blood-flow lateralization data: a new methodology for fTCD analysis

Exploring cerebral laterality of writing and the relationship to handedness: a functional transcranial Doppler ultrasound investigation

Cerebral lateralization of oral language has been investigated in a plethora of studies and it is well established that the left hemisphere is dominant for production tasks in the majority of individuals. However, few studies have focused on written language and even fewer have sampled left-handers. Writing comprises language and motor components, both of which contribute to cerebral activation, yet previous research has not disentangled. The aim of this study was to disentangle the language and motor components of writing lateralization. This was achieved through the comparison of cerebral activation during (i) written word generation and (ii) letter copying, as assessed by functional Transcranial Doppler (fTCD) ultrasound. We further assessed cerebral laterality of oral language. The sample was balanced for handedness. We preregistered the hypotheses that (i) cerebral lateralization of the linguistic component of writing would be weaker in left-handers compared to right-handers and (ii) oral language and the linguistic component of written language would not be correlated in terms of cerebral lateralization. No compelling evidence for either of our hypotheses was found. Findings highlight the complexity of the processes subserving written and oral language as well as the methodological challenges to isolate the linguistic component of writing.

Functional Transcranial Doppler (fTCD) investigation of brain lateralization following visual stimuli

This preliminary investigation of the local cerebral perfusion evaluated by Transcranial Doppler (TCD) monitoring of the Posterior Cerebral Arteries shows that selective stimulation of visual hemifields evokes significantly different vascular responses. TCD can therefore allow for functional evaluation of lateralized enhancements in cerebral metabolism.Clinical Relevance-The cerebral lateralization evaluated with the functional TCD can be a useful and low-cost approach to evaluate the effectiveness of the rehabilitation therapy in post stroke subjects experiencing hemianopia or to assess cerebral reorganization after cerebrovascular accidents.

The scalability of common paradigms for assessment of cognitive function: A functional transcranial Doppler study

Cognitive paradigms induce changes in cerebral blood flow (CBF) associated with increased metabolic demand, namely neurovascular coupling (NVC). We tested the hypothesis that the effect of complexity and duration of cognitive paradigms will either enhance or inhibit the NVC response. Bilateral CBF velocity (CBFV) in the middle cerebral arteries (MCAs) via transcranial Doppler ultrasound (TCD), blood pressure (BP), electrocardiogram (ECG) and end-tidal CO₂ (EtCO₂) of 16 healthy participants (aged 21–71 years) were simultaneously recorded at rest and during randomized paradigms of different complexities (naming words beginning with P-,R-,V- words and serial subtractions of 100–2,100–7,1000–17), and durations (5s, 30s and 60s). CBFV responses were population mean normalized from a 30-s baseline period prior to task initiation. A significant increase in bilateral CBFV response was observed at the start of all paradigms and provided a similar pattern in most responses, irrespective of complexity or duration. Although significant inter-hemispherical differences were found during performance of R-word and all serial subtraction paradigms, no lateralisation was observed in more complex naming word tasks. Also, the effect of duration was manifested at late stages of 100–7, but not for other paradigms. CBFV responses could not distinguish different levels of complexity or duration with a single presentation of the cognitive paradigm. Further studies of the ordinal scalability of the NVC response are needed with more advanced modelling techniques, or different types of neural stimulation.

Cerebrovascular function during cognition in Parkinson's disease: A functional transcranial Doppler sonography study

OBJECTIVE

Recent evidence has linked cerebrovascular abnormalities with Parkinson's Disease (PD), which may provide a new neurophysiological understanding of cognitive impairment in PD. The current study aimed to compare cerebrovascular functioning, during a cognitive task and at rest, in those with and without PD.

METHODS

Idiopathic PD patients (n = 30) and age- and gender-matched healthy controls (n = 30) undertook cognitive testing and completed a word generation task while blood flow velocity was monitored bilaterally with functional transcranial Doppler sonography (fTCD) of the middle cerebral arteries. The lateralisation index and its standard deviation and timing, along with the maximum peak velocity for the left and right hemispheres and their latencies and standard deviations, were calculated for each participant.

RESULTS

The PD patients showed significantly more variability of the lateralisation index compared to the control group; but there were no differences in the lateralisation index itself nor in the peak velocities. In the PD group, the variability in the peak velocities showed significant positive correlations with performance on executive function tests.

CONCLUSION

Normal ageing has been associated with a reduction in the lateralisation index, but no alterations in the standard deviation, suggesting that cerebrovascular functional changes associated with PD differ from those of typical ageing. The within-subject variability observed in the PD group indicate abnormalities within the neurovascular coupling response. Further, the association between the within-subject variability and executive functioning in the PD group, suggests that cerebrovascular dysfunction plays an important role in cognitive impairment in PD.

Musical Attention Control Training for Psychotic Psychiatric Patients: An Experimental Pilot Study in a Forensic Psychiatric Hospital

Poor attention skills constitute a major problem for psychiatric patients with psychotic symptoms, and increase their chances of treatment drop-out. This study investigated possible benefits of musical attention control training (MACT). To examine the effect of MACT on attention skills of psychiatric patients with psychotic features a randomized controlled trial (RCT) was conducted in a forensic psychiatric clinic. Participants (N = 35, age M = 34.7, 69% male) were pair matched (on age, gender, and educational level), and randomly assigned to an experimental and control group. The experimental group received a 30-min MACT training once a week over 6 weeks' time, whereas the controls received treatment as usual without attention training. Single blind pre- and post-neuropsychological assessments were performed to measure different attention levels. The experimental MACT group outperformed the control group in selective, sustained and alternating attention. In addition, overall attendance of MACT participants was high (87.1%). This result suggests that in this experimental pilot study MACT was effective for attention skills of psychiatric patients with psychotic features. To obtain larger intervention effects additional research is necessary, with a larger sample and a more specific MACT intervention.

Music-based interventions in neurological rehabilitation

During the past ten years, an increasing number of controlled studies have assessed the potential rehabilitative effects of music-based interventions, such as music listening, singing, or playing an instrument, in several neurological diseases. Although the number of studies and extent of available evidence is greatest in stroke and dementia, there is also evidence for the effects of music-based interventions on supporting cognition, motor function, or emotional wellbeing in people with Parkinson's disease, epilepsy, or multiple sclerosis. Music-based interventions can affect divergent functions such as motor performance, speech, or cognition in these patient groups. However, the psychological effects and neurobiological mechanisms underlying the effects of music interventions are likely to share common neural systems for reward, arousal, affect regulation, learning, and activity-driven plasticity. Although further controlled studies are needed to establish the efficacy of music in neurological recovery, music-based interventions are emerging as promising rehabilitation strategies.

Functional Transcranial Doppler Ultrasound for Measurement of Hemispheric Lateralization During Visual Memory and Visual Search Cognitive Tasks

Functional transcranial Doppler ultrasound (fTCD) is a noninvasive sensing modality that measures cerebral blood flow velocity (CBFV) with high temporal resolution. CBFV change is correlated to changes in cerebral oxygen uptake, enabling fTCD to measure brain activity and lateralization with high accuracy. However, few studies have examined the relationship of CBFV change during visual search and visual memory tasks. Here a protocol to compare lateralization between these two similar cognitive tasks using fTCD is demonstrated. Ten healthy volunteers (age 21±2 years) were shown visual scenes on a computer and performed visual search and visual memory tasks while CBFV in the bilateral middle cerebral arteries was monitored with fTCD. Each subject completed 40 trials, consisting of baseline (25 s), calibration (variable), instruction (2.5 s), and task (20 s) epochs. Lateralization was computed for each task by calculating the bilateral CBFV envelope percent change from baseline and subtracting the right side from the left side. The results showed significant lateralization ( ) of the visual memory and visual search tasks, with memory reaching lateralization of 1.6% and search reaching lateralization of 0.5%, suggesting that search is more right lateralized (and therefore may be related to "holistic" or global perception) and memory is more left lateralized (and therefore may be related to local perception). This method could be used to compare cerebral activity for any related cognitive tasks as long as the same stimulus is used in all tasks. The protocol is straightforward and the equipment is inexpensive, introducing a low-cost high temporal resolution technique to further study lateralization of the brain.