On Adjusting P-Values for Multiplicity

Westfall, Peter H.; Young, S. Stanley; Wright, S. Paul

doi:10.2307/2532216

Cited by 137 publications

(103 citation statements)

References 15 publications

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“…Subsequently, the signal envelope was extracted by calculating the module of the Hilbert transform. Statistical analysis was performed using the permutation method (Westfall & Young, 1993) with 10,000 iterations. Nonpaired and paired t tests were used for the saline/ketamine factor, and the after-event/ baseline factor, respectively.…”

Section: Discussionmentioning

confidence: 99%

Ketamine Modulates Theta and Gamma Oscillations

Lazarewicz¹,

Ehrlichman²,

Maxwell³

et al. 2010

Journal of Cognitive Neuroscience

196

163

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Ketamine, an N-methyl-D-aspartate (NMDA) receptor glutamatergic antagonist, has been studied as a model of schizophrenia when applied in subanesthetic doses. In EEG studies, ketamine affects sensory gating and alters the oscillatory characteristics of neuronal signals in a complexmanner. We investigated the effects of ketamine on in vivo recordings from the CA3 region of mouse hippocampus referenced to the ipsilateral frontal sinus using a paired-click auditory gating paradigm. One issue of particular interest was elucidating the effect of ketamine on background network activity, poststimulus evoked and induced activity. We find that ketamine attenuates the theta frequency band in both background activity and in poststimulus evoked activity. Ketamine also disrupts a late, poststimulus theta power reduction seen in control recordings. In the gamma frequency range, ketamine enhances both background and evoked power, but decreases relative induced power. These findings support a role for NMDA receptors in mediating the balance between theta and gamma responses to sensory stimuli, with possible implications for dysfunction in schizophrenia. In EEG studies, ketamine affects sensory gating and alters the oscillatory characteristics of neuronal signals in a complex manner. We investigated the effects of ketamine on in vivo recordings from the CA3 region of mouse hippocampus referenced to the ipsilateral frontal sinus using a paired-click auditory gating paradigm. One issue of particular interest was elucidating the effect of ketamine on background network activity, poststimulus evoked and induced activity. We find that ketamine attenuates the theta frequency band in both background activity and in poststimulus evoked activity. Ketamine also disrupts a late, poststimulus theta power reduction seen in control recordings. In the gamma frequency range, ketamine enhances both background and evoked power, but decreases relative induced power. These findings support a role for NMDA receptors in mediating the balance between theta and gamma responses to sensory stimuli, with possible implications for dysfunction in schizophrenia. ■ Disciplines Physical Sciences and Mathematics | Physics

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Section: Discussionmentioning

confidence: 99%

Ketamine Modulates Theta and Gamma Oscillations

Lazarewicz¹,

Ehrlichman²,

Maxwell³

et al. 2010

Journal of Cognitive Neuroscience

196

163

View full text Add to dashboard Cite

show abstract

“…The global hypothesis of independence between the four stand categories and the response variable (number of one or all microhabitats) was assessed using multiple testing of re-sampled data (Westfall and Young 1993;Hothorn et al 2006a). The P value obtained by this procedure was adjusted for multiple comparisons utilizing a step-down max-T approach.…”

Section: Calculations and Statistical Proceduresmentioning

confidence: 99%

Impact of silviculture on dead wood and on the distribution and frequency of tree microhabitats in montane beech-fir forests of the Pyrenees

2011

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In forest ecosystems, the level of biodiversity is strongly linked to dead wood and tree microhabitats. To evaluate the influence of current forest management on the availability of dead wood and on the abundance and distribution of microhabitats, we studied the volume and diversity of dead wood objects and the distribution and frequency of cavities, dendrothelms, cracks, bark losses and sporophores of saproxylic fungi in montane beech-fir stands. We compared stands unmanaged for 50 or 100 years with continuously managed stands. A total of 1,204 live trees and 460 dead wood objects were observed. Total dead wood volume, snag volume and microhabitat diversity were lower in the managed stands, but the total number of microhabitats per ha was not significantly different between managed and unmanaged stands. Cavities were always the most frequent microhabitat and cracks the least frequent. Dendrothelm and bark loss were favored by management. Beech (Fagus sylvatica) carried many more microhabitats than silver fir (Abies alba), especially cavities, dendrothelms and bark losses. Fir very scarcely formed dendrothelms. Secondary tree species played an important role by providing cracks and bark losses. The proportion of microhabitat-bearing trees increased dramatically above circumference thresholds of 225 cm for beech and 215 cm for fir. Firs with a circumference of less than 135 cm did not carry microhabitats. In order to conserve microhabitat-providing trees and to increase the volume of dead wood in managed stands, we recommend conserving trees that finish their natural cycle over 10-20% of the surface area.

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“…This curve provides a statistical value to compare the increase of species with increasing number of plots. Because this curves does not give a significance value, the global hypothesis of independence between the three intensity levels and fungal species richness per plot was assessed by means of resampling-based multiple testing (Westphall and Young 1993). The P-values obtained by this procedure are adjusted for multiple comparisons utilizing a step-down max-T approach (Algorithm 2.8 in Westphall and Young 1993).…”

Section: Data Analysesmentioning

confidence: 99%

Assemblages of wood-inhabiting fungi related to silvicultural management intensity in beech forests in southern Germany

Müller

Engel²,

Blaschke

2007

Eur J Forest Res

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Current silvicultural treatments in beech forests are aimed at achieving thick logs without discoloured hardwood. Therefore intensive thinning is applied already in younger stands with the objective of large-sized trunks at an age of 100 years. However, this approach bears the risk that dead wood structures and broken trees are completely removed from the forest. The impact of three different silvicultural management intensity levels on wood-inhabiting fungi over decades was investigated in a large beech forest (>10,000 ha) in southern Germany in 69 sampling plots: A Intensive Thinning and Logging with high-value trees, B Conservation-Oriented Logging with integration of special structures such as dead wood and broken trees and C Strict Forest Reserves with no logging for 30 years. The analysis of community showed marked differences in the fungus species composition of the three treatments, independent of stand age. The relative frequencies of species between treatments were statistically different. Indicator species for naturalness were more abundant at sites with low silvicultural management intensity. Fomes fomentarius, the most common fungus in virgin forests and strict forest reserves, is almost missing in forests with highmanagement intensity. The species richness seemed to be lower where intensive thinning was applied (P = 0.051). Species characteristic for coarse woody debris were associated to low management intensity, whereas species with a significant preference for stumps became more frequent with increasing management intensity. A total amount of dead wood higher than 60 m 3 /ha was found to enable significantly higher numbers of species indicators of naturalness (P = 0.013). In conclusion, when applying intensive silvicultural treatment, the role of dead wood needs to be actively considered in order to maintain the natural biocoenosis of beech forests.

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On Adjusting P-Values for Multiplicity

Cited by 137 publications

References 15 publications

Ketamine Modulates Theta and Gamma Oscillations

Ketamine Modulates Theta and Gamma Oscillations

Impact of silviculture on dead wood and on the distribution and frequency of tree microhabitats in montane beech-fir forests of the Pyrenees

Assemblages of wood-inhabiting fungi related to silvicultural management intensity in beech forests in southern Germany

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