Sensory computations in the cuneate nucleus of macaques

Tactile nerve fibers fall into a few classes that can be readily distinguished based on their spatiotemporal response properties. Because nerve fibers reflect local skin deformations, they individually carry ambiguous signals about object features. In contrast, cortical neurons exhibit heterogeneous response properties that reflect computations applied to convergent input from multiple classes of afferents, which confer to them a selectivity for behaviorally relevant features of objects. The conventional view is that these complex response properties arise within the cortex itself, implying that sensory signals are not processed to any significant extent in the two intervening structures-the cuneate nucleus (CN) and the thalamus. To test this hypothesis, we recorded the responses evoked in the CN to a battery of stimuli that have been extensively used to characterize tactile coding in both the periphery and cortex, including skin indentations, vibrations, random dot patterns, and scanned edges. We found that CN responses are more similar to their cortical counterparts than they are to their inputs: CN neurons receive input from multiple classes of nerve fibers, they have spatially complex receptive fields, and they exhibit selectivity for object features. Contrary to consensus, then, the CN plays a key role in processing tactile information

Microstimulation of human somatosensory cortex evokes task-dependent, spatially patterned responses in motor cortex

The primary motor (M1) and somatosensory (S1) cortices play critical roles in motor control but the signaling between these structures is poorly understood. To fill this gap, we recorded – in three participants in an ongoing human clinical trial (NCT01894802) for people with paralyzed hands – the responses evoked in the hand and arm representations of M1 during intracortical microstimulation (ICMS) in the hand representation of S1. We found that ICMS of S1 activated some M1 neurons at short, fixed latencies consistent with monosynaptic activation. Additionally, most of the ICMS-evoked responses in M1 were more variable in time, suggesting indirect effects of stimulation. The spatial pattern of M1 activation varied systematically: S1 electrodes that elicited percepts in a finger preferentially activated M1 neurons excited during that finger’s movement. Moreover, the indirect effects of S1 ICMS on M1 were context dependent, such that the magnitude and even sign relative to baseline varied across tasks. We tested the implications of these effects for brain-control of a virtual hand, in which ICMS conveyed tactile feedback. While ICMS-evoked activation of M1 disrupted decoder performance, this disruption was minimized using biomimetic stimulation, which emphasizes contact transients at the onset and offset of grasp, and reduces sustained stimulation

Neural Coding and Sensory Modulation in the Cuneate Nucleus of Primates

The sense of touch is one of our most important channels for communicating with the environment. While vision allows us to identify and locate objects in space, somatosensation is the only sensation that provides direct information about contacting with objects that allows us to interact with them effectively. From picking up a cup to drink, to grasp a pen to write, to touch our loved ones and express our emotions, touch plays an important role in our affective lives and is critical to our ability to dexterously interact with objects. Indeed, tactile feedback is indispensable to make smooth and precise movement execution, patients who lack tactile signals could not achieve smooth motor execution. However, our understanding of tactile processing differs along various stages of the tactile ascending pathway. In primates, the coding of tactile information has been extensively studied in the nerve and in primary somatosensory cortex (S1) while our understanding of the middle structures, the dorsal column nuclei and the thalamus, are limited. Hence, the goal of my dissertation is to investigate how tactile information is represented at the first synapse along the dorsal-column medial lemniscus pathway (DCML), the Cuneate nucleus (CN), that receives tactile and proprioceptive information from the upper body. I characterized the receptive field structure of CN neurons, determined the convergence of input from multiple sensory channels, documented the temporal and spatial processing of information in CN and investigated the state dependence of cutaneous sensitivity in CN. Overall, I gained understanding of the process and calculations happening at this previously neglected region

Reliability and validity of the international dementia alliance schedule for the assessment and staging of care in China

Abstract Background Clinical and social services both are important for dementia care. The International Dementia Alliance (IDEAL) Schedule for the Assessment and Staging of Care was developed to guide clinical and social care for dementia. Our study aimed to assess the validity and reliability of the IDEAL schedule in China. Methods Two hundred eighty-two dementia patients and their caregivers were recruited from 15 hospitals in China. Each patient-caregiver dyad was assessed with the IDEAL schedule by a rater and an observer simultaneously. The Clinical Dementia Rating (CDR), Mini-Mental Status Examination (MMSE), and Caregiver Burden Inventory (CBI) were assessed for criterion validity. IDEAL repeated assessment was conducted 7-10 days after the initial interview for 62 dyads. Results Two hundred seventy-seven patient-caregiver dyads completed the IDEAL assessment. Inter-rater reliability for the total score of the IDEAL schedule was 0.93 (95%CI = 0.92-0.95). The inter-class coefficient for the total score of IDEAL was 0.95 for the interviewers and 0.93 for the silent raters. The IDEAL total score correlated with the global CDR score (ρ = 0.72, p < 0.001), the CDR-sum of box (CDR-SOB, ρ = 0.74, p < 0.001), the total score of MMSE (ρ = −0.65, p < 0.001) and CBI (ρ = 0.70, p < 0.001). All item scores of the IDEAL schedule were associated with the CDR-SOB (ρ = 0.17 ~ 0.79, all p < 0.05). Conclusion The IDEAL schedule is a valid and reliable tool for the staging of care for dementia in the Chinese population

Additional file 3: Table S2. of Reliability and validity of the international dementia alliance schedule for the assessment and staging of care in China

Correlation of item scores of IDEAL, Chinese version, against factor scores of CBI. (DOCX 16 kb

Additional file 2: Table S1. of Reliability and validity of the international dementia alliance schedule for the assessment and staging of care in China

Intra-class correlation coefficients (ICC) for item scores and the total score of IDEAL (test-retest reliability). (DOCX 25 kb

Additional file 1: of Reliability and validity of the international dementia alliance schedule for the assessment and staging of care in China

Study groups, raters and participating hospitals (in alphabetic order by province or administrative city). (DOCX 15 kb