Equivalent noise level generated by drilling onto the ossicular chain as measured by laser Doppler vibrometry: A temporal bone study

Background: Inadvertent drilling on the ossicular chain is one of the causes of sensorineural hearing loss (HL) that may follow tympanomastoid surgery. A high-frequency HL is most frequently observed. It is speculated that the HL is a result of vibration of the ossicular chain resembling acoustic noise trauma. It is generally considered that using a large cutting burr is more likely to cause damage than a small diamond burr. Aim: The aim was to investigate the equivalent noise level and its frequency characteristics generated by drilling onto the short process of the incus in fresh human temporal bones. Methods and Materials: Five fresh cadaveric temporal bones were used. Stapes displacement was measured using laser Doppler vibrometry during short drilling episodes. Diamond. and cutting burrs of different diameters were used. The effect of the drilling on stapes footplate displacement was compared with that generated by an acoustic signal. The equivalent noise level (dB sound pressure level equivalent [SPL eq]) was thus calculated. Results: The equivalent noise levels generated ranged from 93 to 125 dB SPL eq. For a 1-mm cutting burr, the highest equivalent noise level was 108 dB SPL eq, whereas a 2.3-mm cutting burr produced a maximal level of 125 dB SPL eq. Diamond burrs generated less noise than their cutting counterparts, with a 2.3-mm diamond burr producing a highest equivalent noise level of 102, dB SPL eq. The energy of the noise increased at the higher end of the frequency spectrum, with a 2.3-mm cutting burr producing a noise level of 105 dB SPL eq at 1 kHz and 125 dB SPL eq at 8 kHz. In contrast, the same sized diamond burr produced 96 dB SPL eq at 1 kHz and 99 dB at 8 kHz. Conclusion:This study suggests that drilling on the ossicular chain can produce vibratory force that is analogous with noise levels known to produce acoustic trauma. For the same type of burr, the larger the diameter, the greater the vibratory force, and for the same size of burr, the cutting burr creates more vibratory force than the diamond burr. The cutting burr produces greater high-frequency than lower-frequency vibratory energy.

How does the brain mediate interpretation of incongruent auditory emotions? The neural response to prosody in the presence of conflicting lexico-semantic cues

We frequently encounter conflicting emotion cues. This study examined how the neural response to emotional prosody differed in the presence of congruent and incongruent lexico-semantic cues. Two hypotheses were assessed: (i) decoding emotional prosody with conflicting lexico-semantic cues would activate brain regions associated with cognitive conflict (anterior cingulate and dorsolateral prefrontal cortex) or (ii) the increased attentional load of incongruent cues would modulate the activity of regions that decode emotional prosody (right lateral temporal cortex). While the participants indicated the emotion conveyed by prosody, functional magnetic resonance imaging data were acquired on a 3T scanner using blood oxygenation level-dependent contrast. Using SPM5, the response to congruent cues was contrasted with that to emotional prosody alone, as was the response to incongruent lexico-semantic cues (for the 'cognitive conflict' hypothesis). The right lateral temporal lobe region of interest analyses examined modulation of activity in this brain region between these two contrasts (for the 'prosody cortex' hypothesis). Dorsolateral prefrontal and anterior cingulate cortex activity was not observed, and neither was attentional modulation of activity in right lateral temporal cortex activity. However, decoding emotional prosody with incongruent lexico-semantic cues was strongly associated with left inferior frontal gyrus activity. This specialist form of conflict is therefore not processed by the brain using the same neural resources as non-affective cognitive conflict and neither can it be handled by associated sensory cortex alone. The recruitment of inferior frontal cortex may indicate increased semantic processing demands but other contributory functions of this region should be explored.

How the brain blinks: towards a neurocognitive model of the attentional blink

When people monitor a visual stream of rapidly presented stimuli for two targets (T1 and T2), they often miss T2 if it falls into a time window of about half a second after T1 onset-the attentional blink (AB). We provide an overview of recent neuroscientific studies devoted to analyze the neural processes underlying the AB and their temporal dynamics. The available evidence points to an attentional network involving temporal, right-parietal and frontal cortex, and suggests that the components of this neural network interact by means of synchronization and stimulus-induced desynchronization in the beta frequency range. We set up a neurocognitive scenario describing how the AB might emerge and why it depends on the presence of masks and the other event(s) the targets are embedded in. The scenario supports the idea that the AB arises from "biased competition", with the top-down bias being generated by parietal-frontal interactions and the competition taking place between stimulus codes in temporal cortex.

Age-related changes in the functional neuroanatomy of overt speech production

Alterations of existing neural networks during healthy aging, resulting in behavioral deficits and changes in brain activity, have been described for cognitive, motor, and sensory functions. To investigate age-related changes in the neural circuitry underlying overt non-lexical speech production, functional MRI was performed in 14 healthy younger (21–32 years) and 14 healthy older individuals (62–84 years). The experimental task involved the acoustically cued overt production of the vowel /a/ and the polysyllabic utterance /pataka/. In younger and older individuals, overt speech production was associated with the activation of a widespread articulo-phonological network, including the primary motor cortex, the supplementary motor area, the cingulate motor areas, and the posterior superior temporal cortex, similar in the /a/ and /pataka/ condition. An analysis of variance with the factors age and condition revealed a significant main effect of age. Irrespective of the experimental condition, significantly greater activation was found in the bilateral posterior superior temporal cortex, the posterior temporal plane, and the transverse temporal gyri in younger compared to older individuals. Significantly greater activation was found in the bilateral middle temporal gyri, medial frontal gyri, middle frontal gyri, and inferior frontal gyri in older vs. younger individuals. The analysis of variance did not reveal a significant main effect of condition and no significant interaction of age and condition. These results suggest a complex reorganization of neural networks dedicated to the production of speech during healthy aging.

Clustered functional MRI of overt speech production

To investigate the neural network of overt speech production, eventrelated fMRI was performed in 9 young healthy adult volunteers. A clustered image acquisition technique was chosen to minimize speechrelated movement artifacts. Functional images were acquired during the production of oral movements and of speech of increasing complexity (isolated vowel as well as monosyllabic and trisyllabic utterances). This imaging technique and behavioral task enabled depiction of the articulo-phonologic network of speech production from the supplementary motor area at the cranial end to the red nucleus at the caudal end. Speaking a single vowel and performing simple oral movements involved very similar activation of the corticaland subcortical motor systems. More complex, polysyllabic utterances were associated with additional activation in the bilateral cerebellum,reflecting increased demand on speech motor control, and additional activation in the bilateral temporal cortex, reflecting the stronger involvement of phonologic processing.

Revealing and quantifying the impaired phonological analysis underpinning impaired comprehension in Wernicke’s aphasia

Wernicke’s aphasia is a condition which results in severely disrupted language comprehension following a lesion to the left temporo-parietal region. A phonological analysis deficit has traditionally been held to be at the root of the comprehension impairment in WA, a view consistent with current functional neuroimaging which finds areas in the superior temporal cortex responsive to phonological stimuli. However behavioural evidence to support the link between a phonological analysis deficit and auditory comprehension has not been yet shown. This study extends seminal work by Blumstein et al. (1977) to investigate the relationship between acoustic-phonological perception, measured through phonological discrimination, and auditory comprehension in a case series of Wernicke’s aphasia participants. A novel adaptive phonological discrimination task was used to obtain reliable thresholds of the phonological perceptual distance required between nonwords before they could be discriminated. Wernicke’s aphasia participants showed significantly elevated thresholds compared to age and hearing matched control participants. Acoustic-phonological thresholds correlated strongly with auditory comprehension abilities in Wernicke’s aphasia. In contrast, nonverbal semantic skills showed no relationship with auditory comprehension. The results are evaluated in the context of recent neurobiological models of language and suggest that impaired acoustic-phonological perception underlies the comprehension impairment in Wernicke’s aphasia and favour models of language which propose a leftward asymmetry in phonological analysis.

Lesions impairing regular versus irregular past tense production

We investigated selective impairments in the production of regular and irregular past tense by examining language performance and lesion sites in a sample of twelve stroke patients. A disadvantage in regular past tense production was observed in six patients when phonological complexity was greater for regular than irregular verbs, and in three patients when phonological complexity was closely matched across regularity. These deficits were not consistently related to grammatical difficulties or phonological errors but were consistently related to lesion site. All six patients with a regular past tense disadvantage had damage to the left ventral pars opercularis (in the inferior frontal cortex), an area associated with articulatory sequencing in prior functional imaging studies. In addition, those that maintained a disadvantage for regular verbs when phonological complexity was controlled had damage to the left ventral supramarginal gyrus (in the inferior parietal lobe), an area associated with phonological short-term memory. When these frontal and parietal regions were spared in patients who had damage to subcortical (n = 2) or posterior temporo-parietal regions (n = 3), past tense production was relatively unimpaired for both regular and irregular forms. The remaining (12th) patient was impaired in producing regular past tense but was significantly less accurate when producing irregular past tense. This patient had frontal, parietal, subcortical and posterior temporo-parietal damage, but was distinguished from the other patients by damage to the left anterior temporal cortex, an area associated with semantic processing. We consider how our lesion site and behavioral observations have implications for theoretical accounts of past tense production.

Varieties of semantic ‘access’ deficit in Wernicke’s aphasia and semantic aphasia

Comprehension deficits are common in stroke aphasia, including in cases with (i) semantic aphasia (SA), characterised by poor executive control of semantic processing across verbal and nonverbal modalities, and (ii) Wernicke’s aphasia (WA), associated with poor auditory-verbal comprehension and repetition, plus fluent speech with jargon. However, the varieties of these comprehension problems, and their underlying causes, are not well-understood. Both patient groups exhibit some type of semantic ‘access’ deficit, as opposed to the ‘storage’ deficits observed in semantic dementia. Nevertheless, existing descriptions suggest these patients might have different varieties of ‘access’ impairment – related to difficulty resolving competition (in SA) vs. initial activation of concepts from sensory inputs (in WA). We used a case-series design to compare WA and SA patients on Warrington’s paradigmatic assessment of semantic ‘access’ deficits. In these verbal and non-verbal matching tasks, a small set of semantically-related items are repeatedly presented over several cycles so that the target on one trial becomes a distractor on another (building up interference and eliciting semantic ‘blocking’ effects). WA and SA patients were distinguished according to lesion location in the temporal cortex, but in each group, some individuals had additional prefrontal damage. Both of these aspects of lesion variability – one that mapped onto classical ‘syndromes’ and one that did not – predicted aspects of the semantic ‘access’ deficit. Both SA and WA cases showed multimodal semantic impairment, although as expected the WA group showed greater deficits on auditory-verbal than picture judgements. Distribution of damage in the temporal lobe was crucial for predicting the initially beneficial effects of stimulus repetition: WA cases showed initial improvement with repetition of words and pictures, while in SA, semantic access was initially good but declined in the face of competition from previous targets. Prefrontal damage predicted the harmful effects of repetition: the ability to re-select both word and picture targets in the face of mounting competition was linked to left prefrontal damage in both groups. Therefore, SA and WA patients have partially distinct impairment of semantic ‘access’ but, across these syndromes, prefrontal lesions produce declining comprehension with repetition in both verbal and non-verbal tasks.

Bottom-up, not top-down, modulation of imitation by human and robotic models

Visual observation of human actions provokes more motor activation than observation of robotic actions. We investigated the extent to which this visuomotor priming effect is mediated by bottom-up or top-down processing. The bottom-up hypothesis suggests that robotic movements are less effective in activating the ‘mirror system’ via pathways from visual areas via the superior temporal sulcus to parietal and premotor cortices. The top-down hypothesis postulates that beliefs about the animacy of a movement stimulus modulate mirror system activity via descending pathways from areas such as the temporal pole and prefrontal cortex. In an automatic imitation task, subjects performed a prespecified movement (e.g. hand opening) on presentation of a human or robotic hand making a compatible (opening) or incompatible (closing) movement. The speed of responding on compatible trials, compared with incompatible trials, indexed visuomotor priming. In the first experiment, robotic stimuli were constructed by adding a metal and wire ‘wrist’ to a human hand. Questionnaire data indicated that subjects believed these movements to be less animate than those of the human stimuli but the visuomotor priming effects of the human and robotic stimuli did not differ. In the second experiment, when the robotic stimuli were more angular and symmetrical than the human stimuli, human movements elicited more visuomotor priming than the robotic movements. However, the subjects’ beliefs about the animacy of the stimuli did not affect their performance. These results suggest that bottom-up processing is primarily responsible for the visuomotor priming advantage of human stimuli.

Fetal testosterone influences sexually dimorphic gray matter in the human brain

In nonhuman species, testosterone is known to have permanent organizing effects early in life that predict later expression of sex differences in brain and behavior. However, in humans, it is still unknown whether such mechanisms have organizing effects on neural sexual dimorphism. In human males, we show that variation in fetal testosterone (FT) predicts later local gray matter volume of specific brain regions in a direction that is congruent with sexual dimorphism observed in a large independent sample of age-matched males and females from the NIH Pediatric MRI Data Repository. Right temporoparietal junction/posterior superior temporal sulcus (RTPJ/pSTS), planum temporale/parietal operculum (PT/PO), and posterior lateral orbitofrontal cortex (plOFC) had local gray matter volume that was both sexually dimorphic and predicted in a congruent direction by FT. That is, gray matter volume in RTPJ/pSTS was greater for males compared to females and was positively predicted by FT. Conversely, gray matter volume in PT/PO and plOFC was greater in females compared to males and was negatively predicted by FT. Subregions of both amygdala and hypothalamus were also sexually dimorphic in the direction of Male > Female, but were not predicted by FT. However, FT positively predicted gray matter volume of a non-sexually dimorphic subregion of the amygdala. These results bridge a long-standing gap between human and nonhuman species by showing that FT acts as an organizing mechanism for the development of regional sexual dimorphism in the human brain.

Connectivity-based parcellation of the human frontal polar cortex

The frontal pole corresponds to Brodmann area (BA) 10, the largest single architectonic area in the human frontal lobe. Generally, BA10 is thought to contain two or three subregions that subserve broad functions such as multitasking, social cognition, attention, and episodic memory. However, there is a substantial debate about the functional and structural heterogeneity of this large frontal region. Previous connectivity-based parcellation studies have identified two or three subregions in the human frontal pole. Here, we used diffusion tensor imaging to assess structural connectivity of BA10 in 35 healthy subjects and delineated subregions based on this connectivity. This allowed us to determine the correspondence of structurally based subregions with the scheme previously defined functionally. Three subregions could be defined in each subject. However, these three subregions were not spatially consistent between subjects. Therefore, we accepted a solution with two subregions that encompassed the lateral and medial frontal pole. We then examined resting-state functional connectivity of the two subregions and found significant differences between their connectivities. The medial cluster was connected to nodes of the default-mode network, which is implicated in internally focused, self-related thought, and social cognition. The lateral cluster was connected to nodes of the executive control network, associated with directed attention and working memory. These findings support the concept that there are two major anatomical subregions of the frontal pole related to differences in functional connectivity.

A novel component of cannabis extract potentiates excitatory synaptic transmission in rat olfactory cortex in vitro

Cannabis is a potential treatment for epilepsy, although the few human studies supporting this use have proved inconclusive. Previously, we showed that a standardized cannabis extract (SCE), isolated Delta(9)-tetrahydrocannabinol (Delta(9)-THC), and even Delta(9)-THC-free SCE inhibited muscarinic agonist-induced epileptiform bursting in rat olfactory cortical brain slices, acting via CB1 receptors. The present work demonstrates that although Delta(9)-THC (1microM) significantly depressed evoked depolarizing postsynaptic potentials (PSPs) in rat olfactory cortex neurones, both SCE and Delta(9)-THC-free SCE significantly potentiated evoked PSPs (all results were fully reversed by the CB1 receptor antagonist SR141716A, 1microM); interestingly, the potentiation by Delta(9)-THC-free SCE was greater than that produced by SCE. On comparing the effects of Delta(9)-THC-free SCE upon evoked PSPs and artificial PSPs (aPSPs; evoked electrotonically following brief intracellular current injection), PSPs were enhanced, whereas aPSPs were unaffected, suggesting that the effect was not due to changes in background input resistance. Similar recordings made using CB1 receptor-deficient knockout mice (CB1(-/-)) and wild-type littermate controls revealed cannabinoid or extract-induced changes in membrane resistance, cell excitability and synaptic transmission in wild-type mice that were similar to those seen in rat neurones, but no effect on these properties were seen in CB1(-/-) cells. It appears that the unknown extract constituent(s) effects over-rode the suppressive effects of Delta(9)-THC on excitatory neurotransmitter release, which may explain some patients' preference for herbal cannabis rather than isolated Delta(9)-THC (due to attenuation of some of the central Delta(9)-THC side effects) and possibly account for the rare incidence of seizures in some individuals taking cannabis recreationally

For better or for worse, till the human development index do us part?

This paper describes the results of research intended to explore the volatility inherent in the United Nations Development Programme's (UNDP) Human Development Index (HDI). The HDI is intended to be a simple and transparent device for comparing progress in human development, and is an aggregate of life expectancy, education and GDP per capita. Values of the HDI for each country are presented in the Human Development Reports (HDRs), the first being published in 1990. However, while the methodology is consistent for all countries in each year there are notable differences between years that make temporal comparisons of progress difficult. The paper presents the results of recalculating the HDI for a simplified sample of 114 countries using various methodologies employed by the UNDP. The results are a set of deviations of recalculated HDI ranks compared to the original ranks given in the HDRs. The volatility that can result from such recalculation is shown to be substantial (+/-10-15 ranks), yet reports in the popular press are frequently sensitive to movements of only a few ranks. Such movement can easily be accounted for by changes in the HDI methodology rather than genuine progress in human development. While the HDRs often carry warnings about the inadvisability of such year-on-year comparisons, it is argued that the existence of such a high-profile index and the overt presentation within league tables do encourage such comparison. Assuming that the HDI will be retained as a focal point within the HDRs, then it is suggested that greater focus be upon more meaningful and robust categories of human development (e.g. low, medium and high) rather than league tables where shifts of a few places, perhaps as a result of nothing more than a methodological or data artefact, may be highlighted in the press and by policy makers. (C) 2003 Elsevier Science B.V. All rights reserved.

Organizational effects of fetal testosterone on human corpus callosum size and asymmetry

Previous theory and research in animals has identified the critical role that fetal testosterone (FT) plays in organizing sexually dimorphic brain development. However, to date there are no studies in humans directly testing the organizational effects of FT on structural brain development. In the current study we investigated the effects of FT on corpus callosum size and asymmetry. High-resolution structural magnetic resonance images (MRI) of the brain were obtained on 28 8-11-year-old boys whose exposure to FT had been previously measured in utero via amniocentesis conducted during the second trimester. Although there was no relationship between FT and midsaggital corpus callosum size, increasing FT was significantly related to increasing rightward asymmetry (e.g., Right>Left) of a posterior subsection of the callosum, the isthmus, that projects mainly to parietal and superior temporal areas. This potential organizational effect of FT on rightward callosal asymmetry may be working through enhancing the neuroprotective effects of FT and result in an asymmetric distribution of callosal axons. We suggest that this possible organizational effect of FT on callosal asymmetry may also play a role in shaping sexual dimorphism in functional and structural brain development, cognition, and behavior.

Regional response differences across the human amygdaloid complex during social conditioning

The amygdala is consistently implicated in biologically relevant learning tasks such as Pavlovian conditioning. In humans, the ability to identify individual faces based on the social outcomes they have predicted in the past constitutes a critical form of associative learning that can be likened to “social conditioning.” To capture such learning in a laboratory setting, participants learned about faces that predicted negative, positive, or neutral social outcomes. Participants reported liking or disliking the faces in accordance with their learned social value. During acquisition, we observed differential functional magnetic resonance imaging activation across the human amygdaloid complex consistent with previous lesion, electrophysiological, and functional neuroimaging data. A region of the medial ventral amygdala and a region of the dorsal amygdala/substantia innominata showed signal increases to both Negative and Positive faces, whereas a lateral ventral region displayed a linear representation of the valence of faces such that Negative > Positive > Neutral. This lateral ventral locus also differed from the dorsal and medial loci in that the magnitude of these responses was more resistant to habituation. These findings document a role for the human amygdala in social learning and reveal coarse regional dissociations in amygdala activity that are consistent with previous human and nonhuman animal data.