MEG-measured visually induced gamma-band oscillations in chronic schizophrenia: Evidence for impaired generation of rhythmic activity in ventral stream regions

Background: Gamma-band oscillations are prominently impaired in schizophrenia, but the nature of the deficit and relationship to perceptual processes is unclear. Methods: 16 patients with chronic schizophrenia (ScZ) and 16 age-matched healthy controls completed a visual paradigm while magnetoencephalographic (MEG) data was recorded. Participants had to detect randomly occurring stimulus acceleration while viewing a concentric moving grating. MEG data were analyzed for spectral power (1-100 Hz) at sensorand source-level to examine the brain regions involved in aberrant rhythmic activity, and for contribution of differences in baseline activity towards the generation of low- and highfrequency power. Results: Our data show reduced gamma-band power at sensor level in schizophrenia patients during stimulus processing while alpha-band and baseline spectrum were intact. Differences in oscillatory activity correlated with reduced behavioral detection rates in the schizophrenia group and higher scores on the “Cognitive Factor” of the Positive and Negative Syndrome Scale. Source reconstruction revealed that extra-striate (fusiform/lingual gyrus), but not striate (cuneus), visual cortices contributed towards the reduced activity observed at sensorlevel in ScZ patients. Importantly, differences in stimulus-related activity were not due to differences in baseline activity. Conclusions: Our findings highlight that MEG-measured high-frequency oscillations during visual processing can be robustly identified in ScZ. Our data further suggest impairments that involve dysfunctions in ventral stream processing and a failure to increase gamma-band activity in a task-context. Implications of these findings are discussed in the context of current theories of cortical-subcortical circuit dysfunctions and perceptual processing in ScZ.

Peat Bog Ecosystems: Tracks across peatlands

Tracks have been made across peatlands for as long as human society has existed. Un - made tracks (i.e. those created simply by regular use, with no construction involved) were probably first created by grazing animals and then presumably also used by early human communities. F ind ing these increasingly impassable with regular use , human societies began to construct ' corduroy roads ' during Neolithic, Bronze and Iron Age times. These first constructed tracks were made from cut timbers ( below ) . Across Europe, ma ny examples of these corduroy roads have been found preserved in lowland bogs, perhaps most famously in the Somerset Levels and more recently at Hatfield Moors on the Humberhead Levels.

Peat Bog Ecosystems: Peatland Restoration

Peatland restoration involves giving aid to a complex ecosystem which has been damaged in some way. A reasonable analogy is a patient brought to a hospital for urgent treatment. When arriving at Accident & Emergency , the first priority of the medical team is to stabilise the patient’s condition. Only after the patient’s condition has been assessed and then stabilised can the team begin to think about the longer - term process of healing and recovery. A similar logic is applied to peatland s . First , stabilisation is required to prevent further degradation, following which restoration can focus on the recovery of the ecosystem.

Peat Bog Ecosystems: Atmospheric pollution

Peatlands can be damaged by deposition of pollutants from the atmosphere – often termed ‘ acid rain ’ . This results from the release of sulphur and nitrogen pollutants into the atmosphere . Originally associated with the Industrial Revolution, ‘acid rain’ was first described by Robert Angus Smith, a Manchester chemist of the 1800s , whose obser vations were made in close proximity to the peatlands of the South Pennines. Sulphur dioxide (SO 2 ) pollution, which is mainly emitted from coal burning power stations, peaked in the 1970s and has since decreased by over 90% due to emission controls and ch anges in energy supply. N itrogen ous air pollutants have decreased less . N itrogen oxide (NO x ) emissions , which are mainly from vehicle s , have decreased by two thirds since their peak in 1990 , but the decrease in ammonia ( NH 3 ) emissions , which are mainly from intensive livestock farming, is much less certain and may be only about 20%.