Luke A. Henderson

Bio: Luke A. Henderson is an academic researcher from University of Sydney. The author has contributed to research in topics: Chronic pain & Neuropathic pain. The author has an hindex of 41, co-authored 135 publications receiving 5942 citations. Previous affiliations of Luke A. Henderson include University of California, Los Angeles & Prince of Wales Medical Research Institute.

Autonomic markers of emotional processing: skin sympathetic nerve activity in humans during exposure to emotionally charged images.

Abstract: The sympathetic innervation of the skin primarily subserves thermoregulation, but the system has also been commandeered as a means of expressing emotion. While it is known that the level of skin sympathetic nerve activity (SSNA) is affected by anxiety, the majority of emotional studies have utilized the galvanic skin response as a means of inferring increases in SSNA. The purpose of the present study was to characterize the changes in SSNA when showing subjects neutral or emotionally-charged images from the International Affective Picture System. Skin sympathetic nerve activity was recorded via tungsten microelectrodes inserted into cutaneous fascicles of the common peroneal nerve in ten subjects. Neutral images, positively-charged images (erotica) or negatively-charged images (mutilation) were presented in blocks of fifteen images of a specific type, each block lasting two minutes. Images of erotica or mutilation were presented in a quasi-random fashion, each block following a block of neutral images. Both images of erotica or images of mutilation caused significant increases in SSNA, but the increases in SSNA were greater for mutilation. The increases in SSNA were often coupled with sweat release and cutaneous vasoconstriction, however, these markers were not always consistent with the SSNA increases. We conclude that SSNA, comprising cutaneous vasoconstrictor and sudomotor activity, increases with both positively-charged and negatively-charged emotional images. Measurement of SSNA provides a more comprehensive assessment of sympathetic outflow to the skin than does the use of sweat release alone as a marker of emotional processing.

Brain Morphology Associated with Obstructive Sleep Apnea

Abstract: Obstructive sleep apnea (OSA) is characterized by repeated occurrences of hypoxic, hypercapnic, and transient blood pressure elevation episodes that may damage or alter neural structures. Underdeveloped structures or pre-existing damage in brain areas may also contribute to the genesis of the syndrome. Brain morphology in 21 patients with OSA and in 21 control subjects was assessed using high-resolution T1-weighted magnetic resonance imaging. Three-dimensional brain images were obtained with voxels of approximately 1 mm3. Images were spatially normalized and segmented into gray matter, white matter, and cerebrospinal fluid. For each segment, regional volumetric differences were determined relative to age, handedness, and group (patients with OSA versus control subjects), using voxel-based morphometry, with OSA effects weighted by disease severity. A significant age effect on total gray matter was found in control subjects but not in patients with OSA. Diminished regional and often unilateral gray matter l...

Neuropathic pain and primary somatosensory cortex reorganization following spinal cord injury.

Abstract: The most obvious impairments associated with spinal cord injury (SCI) are loss of sensation and motor control. However, many subjects with SCI also develop persistent neuropathic pain below the injury which is often severe, debilitating and refractory to treatment. The underlying mechanisms of persistent neuropathic SCI pain remain poorly understood. Reports in amputees describing phantom limb pain demonstrate a positive correlation between pain intensity and the amount of primary somatosensory cortex (S1) reorganization. Of note, this S1 reorganization has also been shown to reverse with pain reduction. It is unknown whether a similar association between S1 reorganization and pain intensity exists in subjects with SCI. The aim of this investigation was to determine whether the degree of S1 reorganization following SCI correlated with on-going neuropathic pain intensity. In 20 complete SCI subjects (10 with neuropathic pain, 10 without neuropathic pain) and 21 control subjects without SCI, the somatosensory cortex was mapped using functional magnetic resonance imaging during light brushing of the right little finger, thumb and lip. S1 reorganization was demonstrated in SCI subjects with the little finger activation point moving medially towards the S1 region that would normally innervate the legs. The amount of S1 reorganization in subjects with SCI significantly correlated with on-going pain intensity levels. This study provides evidence of a link between the degree of cortical reorganization and the intensity of persistent neuropathic pain following SCI. Strategies aimed at reversing somatosensory cortical reorganization may have therapeutic potential in central neuropathic pain.

Anatomical Changes in Human Motor Cortex and Motor Pathways following Complete Thoracic Spinal Cord Injury

Abstract: A debilitating consequence of complete spinal cord injury (SCI) is the loss of motor control. Although the goal of most SCI treatments is to re-establish neural connections, a potential complication in restoring motor function is that SCI may result in anatomical and functional changes in brain areas controlling motor output. Some animal investigations show cell death in the primary motor cortex following SCI, but similar anatomical changes in humans are not yet established. The aim of this investigation was to use voxel-based morphometry (VBM) and diffusion tensor imaging (DTI) to determine if SCI in humans results in anatomical changes within motor cortices and descending motor pathways. Using VBM, we found significantly lower gray matter volume in complete SCI subjects compared with controls in the primary motor cortex, the medial prefrontal, and adjacent anterior cingulate cortices. DTI analysis revealed structural abnormalities in the same areas with reduced gray matter volume and in the superior cerebellar cortex. In addition, tractography revealed structural abnormalities in the corticospinal and corticopontine tracts of the SCI subjects. In conclusion, human subjects with complete SCI show structural changes in cortical motor regions and descending motor tracts, and these brain anatomical changes may limit motor recovery following SCI.

Different Pain, Different Brain: Thalamic Anatomy in Neuropathic and Non-Neuropathic Chronic Pain Syndromes

Abstract: Trigeminal neuropathic pain (TNP) and temporomandibular disorders (TMD) are thought to have fundamentally different etiologies. It has been proposed that TNP arises through damage to, or pressure on, somatosensory afferents in the trigeminal nerve, whereas TMD results primarily from peripheral nociceptor activation. Because some reports suggest that neuropathic pain is associated with changes in brain anatomy, it is possible that TNP is maintained by changes in higher brain structures, whereas TMD is not. The aim of this investigation is to determine whether changes in regional brain anatomy and biochemistry occur in both conditions. Twenty-one TNP subjects, 20 TMD subjects, and 36 healthy controls were recruited. Voxel-based morphometry of T1-weighted anatomical images revealed no significant regional gray matter volume change in TMD patients. In contrast, gray matter volume of TNP patients was reduced in the primary somatosensory cortex, anterior insula, putamen, nucleus accumbens, and the thalamus, whereas gray matter volume was increased in the posterior insula. The thalamic volume decrease was only seen in the TNP patients classified as having trigeminal neuropathy but not those with trigeminal neuralgia. Furthermore, in trigeminal neuropathy patients, magnetic resonance spectroscopy revealed a significant reduction in the N-acetylaspartate/creatine ratio, a biochemical marker of neural viability, in the region of thalamic volume loss. The data suggest that the pathogenesis underlying neuropathic and non-neuropathic pain conditions are fundamentally different and that neuropathic pain conditions that result from peripheral injuries may be generated and/or maintained by structural changes in regions such as the thalamus.

How do you feel--now? The anterior insula and human awareness.

Abstract: The anterior insular cortex (AIC) is implicated in a wide range of conditions and behaviours, from bowel distension and orgasm, to cigarette craving and maternal love, to decision making and sudden insight. Its function in the re-representation of interoception offers one possible basis for its involvement in all subjective feelings. New findings suggest a fundamental role for the AIC (and the von Economo neurons it contains) in awareness, and thus it needs to be considered as a potential neural correlate of consciousness.

Pathophysiology of Sleep Apnea

Abstract: Sleep-induced apnea and disordered breathing refers to intermittent, cyclical cessations or reductions of airflow, with or without obstructions of the upper airway (OSA). In the presence of an anat...