Browsing by Subject "PRECISION"

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  • Yurtseva, Anastasia; Noreikiene, Kristina; Lajus, Dmitry; Li, Zitong; Alapassi, Tarja; Ivanova, Tatiana; Ivanov, Mikhail; Golovin, Pavel; Vesala, Sami; Merilä, Juha (2019)
    In order to assess the accuracy and reliability of age estimates from calcified structures in the three-spined stickleback Gasterosteus aculeatus, we evaluated intra and inter-reader repeatability from three structures: otoliths, gill covers and pelvic spines). Average age estimates were also compared between the structures. The overall intra-reader repeatability of age estimates were highest for otoliths (69%), lowest for gill covers (53%) and intermediate for spine cross-sections (63%). Although four of the seven readers had the highest intra-reader repeatability score for spine cross-sections, the inter-reader variance in this structure was much higher than in others. Otoliths were the easiest in terms of their pre-analysis treatment and exchange of materials (as digital images) between readers. In addition, otoliths are more well-studied compared with the other structures with respect to their development through ontogenesis; hence, age estimates based on otoliths should be the most reliable. Therefore, our recommendation is that whenever possible, analysis of otoliths should be the preferred approach for aging G. aculeatus.
  • Eyherabide, Hugo Gabriel; Samengo, Ines (2018)
    The study of the neural code aims at deciphering how the nervous system maps external stimuli into neural activitythe encoding phaseand subsequently transforms such activity into adequate responses to the original stimulithe decoding phase. Several information-theoretical methods have been proposed to assess the relevance of individual response features, as for example, the spike count of a given neuron, or the amount of correlation in the activity of two cells. These methods work under the premise that the relevance of a feature is reflected in the information loss that is induced by eliminating the feature from the response. The alternative methods differ in the procedure by which the tested feature is removed, and the algorithm with which the lost information is calculated. Here we compare these methods, and show that more often than not, each method assigns a different relevance to the tested feature. We demonstrate that the differences are both quantitative and qualitative, and connect them with the method employed to remove the tested feature, as well as the procedure to calculate the lost information. By studying a collection of carefully designed examples, and working on analytic derivations, we identify the conditions under which the relevance of features diagnosed by different methods can be ranked, or sometimes even equated. The condition for equality involves both the amount and the type of information contributed by the tested feature. We conclude that the quest for relevant response features is more delicate than previously thought, and may yield to multiple answers depending on methodological subtleties.
  • Aikio, R.; Laaksonen, K.; Sairanen, A; Parkkonen, E.; Abou Elseoud, A.; Kujala, J.; Forss, N. (2021)
    In healthy subjects, motor cortex activity and electromyographic (EMG) signals from contracting contralateral muscle show coherence in the beta (15-30 Hz) range. Corticomuscular coherence (CMC) is considered a sign of functional coupling between muscle and brain. Based on prior studies, CMC is altered in stroke, but functional significance of this finding has remained unclear. Here, we examined CMC in acute stroke patients and correlated the results with clinical outcome measures and corticospinal tract (CST) integrity estimated with diffusion tensor imaging (DTI). During isometric contraction of the extensor carpi radialis muscle, EMG and magneto encephalographic oscillatory signals were recorded from 29 patients with paresis of the upper extremity due to ischemic stroke and 22 control subjects. CMC amplitudes and peak frequencies at 13-30 Hz were compared between the two groups. In the patients, the peak frequency in both the affected and the unaffected hemisphere was significantly (p < 0.01) lower and the strength of CMC was significantly (p < 0.05) weaker in the affected hemisphere compared to the control subjects. The strength of CMC in the patients correlated with the level of tactile sensitivity and clinical test results of hand function. In contrast, no correlation between measures of CST integrity and CMC was found. The results confirm the earlier findings that CMC is altered in acute stroke and demonstrate that CMC is bidirectional and not solely a measure of integrity of the efferent corticospinal tract.
  • Vastaranta, Mikko; Latorre, Eduardo Gonzalez; Luoma, Ville; Saarinen, Ninni; Holopainen, Markus; Hyyppä, Juha (2015)
    We evaluated a smartphone app (TRESTIMA(TM)) for forest sample plot measurements. The app interprets imagery collected from the sample plots using the camera in the smartphone and then estimates forest inventory attributes, including species-specific basal areas (G) as well as the diameter (D-gM) and height (H-gM) of basal area median trees. The estimates from the smartphone app were compared to forest inventory attributes derived from tree-wise measurements using calipers and a Vertex height measurement device. The data consist of 2169 measured trees from 25 sample plots (32 m x 32 m), dominated by Scots pine and Norway spruce from southern Finland. The root-mean-square errors (RMSEs) in the basal area varied from 19.7% to 29.3% and the biases from 11.4% to 18.4% depending on the number of images per sample plot and image shooting location. D-gM measurement bias varied from -1.4% to 3.1% and RMSE from 5.2% to 11.6% depending on the tree species. Respectively, H-gM bias varied from 5.0% to 8.3% and RMSE 10.0% to 13.6%. In general, four images captured toward the center of the plot provided more accurate results than four images captured away from the plot center. Increasing the number of captured images per plot to the analyses yielded only marginal improvement to the results.
  • Ölander, K.; Muukkonen, I.; Saarela, T. P.; Salmela, V. R. (2019)
    Simple visual items and complex real-world objects are stored into visual working memory as a collection of independent features, not as whole or integrated objects. Storing faces into memory might differ, however, since previous studies have reported perceptual and memory advantage for whole faces compared to other objects. We investigated whether facial features can be integrated in a statistically optimal fashion and whether memory maintenance disrupts this integration. The observers adjusted a probe - either a whole face or isolated features (eyes or mouth region) - to match the identity of a target while viewing both stimuli simultaneously or after a 1.5 second retention period. Precision was better for the whole face compared to the isolated features. Perceptual precision was higher than memory precision, as expected, and memory precision further declined as the number of memorized items was increased from one to four. Interestingly, the whole-face precision was better predicted by models assuming injection of memory noise followed by integration of features than by models assuming integration of features followed by the memory noise. The results suggest equally weighted or optimal integration of facial features and indicate that feature information is preserved in visual working memory while remembering faces.
  • Collett, Thomas; Montanari, Francesco; Räsänen, Syksy (2019)
    We present the first determination of the Hubble constant H-0 from strong lensing time delay data and type Ia supernova luminosity distances that is independent of the cosmological model. We also determine the spatial curvature model independently. We assume that light propagation over long distances is described by the Friedmann-Lemaitre-Robertson-Walker (FLRW) metric and geometrical optics holds, but make no assumption about the contents of the Universe or the theory of gravity on cosmological scales. We find H-0 = 75.7(-4.4)(+4.5) km/s/Mpc and Omega(K0) = 0.12(-0.25)(+0.27). This is a 6% determination of H-0. A weak prior from the cosmic microwave background on the distance to the last scattering surface improves this to H-0 = 76.8(-3.8)(+4.2) km/s/Mpc and Omega(K0) = 0.18(-0.18)(+0.25). Assuming a zero spatial curvature, we get H-0 = 74.2(-2.9)(+3.0) km/s/Mpc, a precision of 4%. The measurements also provide a consistency test of the FLRW metric: we find no evidence against it.
  • Salmela, Viljami R.; Ölander, Kaisu; Muukkonen, Ilkka; Bays, Paul M. (2019)
    Many studies of visual working memory have tested humans' ability to reproduce primary visual features of simple objects, such as the orientation of a grating or the hue of a color patch, following a delay. A consistent finding of such studies is that precision of responses declines as the number of items in memory increases. Here we compared visual working memory for primary features and high-level objects. We presented participants with memory arrays consisting of oriented gratings, facial expressions, or a mixture of both. Precision of reproduction for all facial expressions declined steadily as the memory load was increased from one to five faces. For primary features, this decline and the specific distributions of error observed, have been parsimoniously explained in terms of neural population codes. We adapted the population coding model for circular variables to the non-circular and bounded parameter space used for expression estimation. Total population activity was held constant according to the principle of normalization and the intensity of expression was decoded by drawing samples from the Bayesian posterior distribution. The model fit the data well, showing that principles of population coding can be applied to model memory representations at multiple levels of the visual hierarchy. When both gratings and faces had to be remembered, an asymmetry was observed. Increasing the number of faces decreased precision of orientation recall, but increasing the number of gratings did not affect recall of expression, suggesting that memorizing faces involves the automatic encoding of low-level features, in addition to higher-level expression information.
  • Salmela, Viljami R.; Lähde, Meri; Saarinen, Jussi (2012)
  • Phriksee, Anirut; Jullo, Eric; Limousin, Marceau; Shan, HuanYuan; Finoguenov, Alexis; Komonjinda, Siramas; Wannawichian, Suwicha; Sawangwit, Utane (2020)
    We present the weak-lensing analysis of 279 CODEX clusters using imaging data from 4200 deg(2) of the DECam Legacy Survey (DECaLS) Data Release 3. The cluster sample results from a joint selection in X-ray, optical richness in the range 20 proportional to M-0 (lambda/40)(F lambda). By measuring the CODEX cluster sample as an individual cluster, we obtain the best-fitting values, M-0 = 3.24(-0.27)(+0.29) x 10(14)M(circle dot), and F-lambda = 1.00(-0.22)(+0.22) for the richness scaling index, consistent with a power-law relation. Moreover, we separate the cluster sample into three richness groups; lambda = 20-30, 30-50, and 50-110, and measure the stacked excess surface mass density profile in each group. The results show that both methods are consistent. In addition, we find an excellent agreement between our weak lensing based scaling relation and the relation obtained with dynamical masses estimated from cluster member velocity dispersions measured by the SDSS-IV/SPIDERS team. This suggests that the cluster dynamical equilibrium assumption involved in the dynamical mass estimates is statistically robust for a large sample of clusters.