Mechanisms of change in the evolution of jargon aphasia

Background: The evolution of jargon aphasia may reflect recovery in the speech production processes. Alternatively or additionally there may be improved self-monitoring, enabling the person to suppress jargon errors. Previous case reports offer evidence for both mechanisms of change, and suggest that they can co-occur. Aims: This longitudinal study aimed to uncover mechanisms of change in an individual with jargon aphasia. Four predictions of production processing recovery were examined against test data. The study also looked for evidence of improved error awareness, in both test and connected speech data, and explored the relationship between this improvement and the production gains. Methods & Procedures: The participant (TK) undertook tests of single word naming, reading and repetition eight times over a 21-month period, with matched sets of nouns and verbs. Analyses of correct responses and errors were conducted, in order to test predictions of processing recovery. Changes in self-monitoring behaviours were also investigated, to uncover evidence of increased error awareness. Finally, longitudinal changes in samples of connected speech were explored. Outcomes & Results: Two predictions of production processing recovery were upheld: there was a significant increase in the number of correct responses over time, and a significant decrease in the proportion of nonword errors. The error analysis also revealed a trend towards increased target-relatedness and decreased perseveration, but neither was significant. There was an increase in self-monitoring behaviours during testing, in that there were more null responses and attempted self-corrections. This increase correlated very strongly with the production gains. Connected speech showed little evidence of improved production, since the range of vocabulary employed by TK reduced as time progressed. However, self-monitoring behaviours were increasingly evident in this context. Conclusions: The origin of the production and monitoring gains experienced by TK are discussed. Implications are drawn out for further research

Principles and Fundamentals of Optical Imaging

In this chapter I will give a brief general introduction to optical imaging and then discuss in more detail some of the methods specifically used for imaging cortical dynamics today. Absorption and fluorescence microscopy can be used to form direct, diffraction-limited images but standard methods are often only applicable to superficial layers of cortical tissue. Two-photon microscopy takes an intermediate role since the illumination pathway is diffraction-limited but the detection pathway is not. Losses in the illumination path can be compensated using higher laser power. Since the detection pathway does not require image formation, the method can substantially increase the imaging depth. Understanding the role of scattering is important in this case since non-descanned detection can substantially enhance the imaging performance. Finally, I will discuss some of the most widely used imaging methods that all rely on diffuse scattering such as diffuse optical tomography, laser speckle imaging, and intrinsic optical imaging. These purely scattering-based methods offer a much higher imaging depth, although at a substantially reduced spatial resolution

Whole-scalp EEG mapping of somatosensory evoked potentials in macaque monkeys

High-density scalp EEG recordings are widely used to study whole-brain neuronal networks in humans non-invasively. Here, we validate EEG mapping of somatosensory evoked potentials (SSEPs) in macaque monkeys (Macaca fascicularis) for the long-term investigation of large-scale neuronal networks and their reorganisation after lesions requiring a craniotomy. SSEPs were acquired from 33 scalp electrodes in five adult anaesthetized animals after electrical median or tibial nerve stimulation. SSEP scalp potential maps were identified by cluster analysis and identified in individual recordings. A distributed, linear inverse solution was used to estimate the intracortical sources of the scalp potentials. SSEPs were characterised by a sequence of components with unique scalp topographies. Source analysis confirmed that median nerve SSEP component maps were in accordance with the somatotopic organisation of the sensorimotor cortex. Most importantly, SSEP recordings were stable both intra- and interindividually. We aim to apply this method to the study of recovery and reorganisation of large-scale neuronal networks following a focal cortical lesion requiring a craniotomy. As a prerequisite, the present study demonstrated that a 300-mm2 unilateral craniotomy over the sensorimotor cortex necessary to induce a cortical lesion, followed by bone flap repositioning, suture and gap plugging with calcium phosphate cement, did not induce major distortions of the SSEPs. In conclusion, SSEPs can be successfully and reproducibly recorded from high-density EEG caps in macaque monkeys before and after a craniotomy, opening new possibilities for the long-term follow-up of the cortical reorganisation of large-scale networks in macaque monkeys after a cortical lesion