Need for risk-adapted therapy for malignant ovarian germ cell tumors: A large multicenter analysis of germ cell tumors' patients from French TMRG network.

BACKGROUND: Malignant ovarian germ cell tumors are rare tumors, affecting young women with a generally favorable prognosis. The French reference network for Rare Malignant Gynecological Tumors (TMRG) aims to improve their management. The purpose of this study is to report clinicopathological features and long-term outcomes, to explore prognostic parameters and to help in considering adjuvant strategy for stage I patients. PATIENTS AND METHODS: Data from patients with MOGCT registered among 13 of the largest centers of the TMRG network were analyzed. We report clinicopathological features, estimated 5-year event-free survival (5y-EFS) and 5-year overall survival (5y-OS) of MOGCT patients. RESULTS: We collected data from 147 patients including 101 (68.7%) FIGO stage I patients. Histology identifies 40 dysgerminomas, 52 immature teratomas, 32 yolk sac tumors, 2 choriocarcinomas and 21 mixed tumors. Surgery was performed in 140 (95.2%) patients and 106 (72.1%) received first line chemotherapy. Twenty-two stage I patients did not receive chemotherapy. Relapse occurred in 24 patients: 13 were exclusively treated with upfront surgery and 11 received surgery and chemotherapy. 5y-EFS was 82% and 5y-OS was 92.4%. Stage I patients who underwent surgery alone had an estimated 5y-EFS of 54.6% and patients receiving adjuvant chemotherapy 94.4% (P < .001). However, no impact on estimated 5y-OS was observed: 96.3% versus 97.8% respectively (P = .62). FIGO stage, complete primary surgery and post-operative alpha fetoprotein level significantly correlated with survival. CONCLUSION: Adjuvant chemotherapy does not seem to improve survival in stage I patients. Active surveillance can be proposed for selected patients with a complete surgical staging.

Clinical validation of a prognostic tool in a population of outpatients treated for incurable cancer undergoing anticancer therapy: PRONOPALL study.

BACKGROUND: In 2008, a study of the characteristics of hospitalised patients led to the development of a prognostic tool that distinguished three populations with significantly different 2-month survival rates. The goal of our study aimed at validating prospectively this prognostic tool in outpatients treated for cancer in terminal stage, based on four factors: performance status (ECOG) (PS), number of metastatic sites, serum albumin and lactate dehydrogenase. PATIENTS AND METHODS: PRONOPALL is a multicentre study of current care. About 302 adult patients who met one or more of the following criteria: life expectancy under 6 months, performance status ≥ 2 and disease progression during the previous chemotherapy regimen were included across 16 institutions between October 2009 and October 2010. Afterwards, in order to validate the prognostic tool, the score was ciphered and correlated to patient survival. RESULTS: Totally 262 patients (87%) were evaluable (27 patients excluded and 13 unknown score). Median age was 66 years [37-88], and women accounted for 59%. ECOG PS 0-1 (46%), PS 2 (37%) and PS 3-4 (17%). The primary tumours were: breast (29%), colorectal (28%), lung (13%), pancreas (12%), ovary (11%) and other (8%). About 32% of patients presented one metastatic site, 35% had two and 31% had more than two. The median lactate dehydrogenase level was 398 IU/l [118-4314]; median serum albumin was 35 g/l [13-54]. According to the PRONOPALL prognostic tool, the 2-month survival rate was 92% and the median survival rate was 301 days [209-348] for the 130 patients in population C, 66% and 79 days [71-114] for the 111 patients in population B, and 24% and 35 days for [14-56] the 21 patients in population A. These three populations survival were statistically different (P <0.0001). CONCLUSION: PRONOPALL study confirms the three prognostic profiles defined by the combination of four factors. This PRONOPALL score is a useful decision-making tool in daily practice.

A Neural Substrate for Rapid Timbre Recognition? Neural and Behavioral Discrimination of Very Brief Acoustic Vowels.

The timbre of a sound plays an important role in our ability to discriminate between behaviorally relevant auditory categories, such as different vowels in speech. Here, we investigated, in the primary auditory cortex (A1) of anesthetized guinea pigs, the neural representation of vowels with impoverished timbre cues. Five different vowels were presented with durations ranging from 2 to 128 ms. A psychophysical experiment involving human listeners showed that identification performance was near ceiling for the longer durations and degraded close to chance level for the shortest durations. This was likely due to spectral splatter, which reduced the contrast between the spectral profiles of the vowels at short durations. Effects of vowel duration on cortical responses were well predicted by the linear frequency responses of A1 neurons. Using mutual information, we found that auditory cortical neurons in the guinea pig could be used to reliably identify several vowels for all durations. Information carried by each cortical site was low on average, but the population code was accurate even for durations where human behavioral performance was poor. These results suggest that a place population code is available at the level of A1 to encode spectral profile cues for even very short sounds.

Intra-arterial yttrium-90 radioembolization combined with systemic chemotherapy is a promising method for downstaging unresectable huge intrahepatic cholangiocarcinoma to surgical treatment.

PURPOSE: To evaluate the downstaging efficacy of yttrium-90 radioembolization (Ytt-90)-associated with chemotherapy and the results of surgery for initially unresectable huge intrahepatic cholangiocarcinoma (ICC). METHODS: Between January 2008 and October 2013, unresectable ICC were treated with chemotherapy and Ytt-90. Patients with unique tumors localized to noncirrhotic livers and without extrahepatic metastasis were considered to be potentially resectable and were evaluated every 2 months for possible secondary resection. RESULTS: Forty-five patients were treated for unresectable ICCs; ten had potentially resectable tumors, and eight underwent surgery. Initial unresectability was due to the involvement of the hepatic veins or portal vein of the future liver remnant in seven and one cases, respectively. Preoperative treatment induced significant decreases in tumor volume (295 vs. 168 ml, p = 0.02) and allowed for R0 resection in all cases. Three patients (37.5 %) had Clavien-Dindo grade three or higher complications, including two postoperative deaths. The median follow-ups were 15.6 [range 4-40.7] months after medical treatment initiation and 7.2 [0.13-36.4] months after surgery. At the end of the study period, five patients were still alive, with one patient still alive 40 months after medical treatment initiation (36.4 months after surgery); two patients experienced recurrences. CONCLUSIONS: For initially unresectable huge ICCs, chemotherapy with Ytt-90 radioembolization is an effective downstaging method that allows for secondary resectability.

Asymmetric pulses delivered by a cochlear implant allow a reduction in evoked firing rate and in spatial activation in the guinea pig auditory cortex.

Despite that fact that the cochlear implant (CI) is one of the most successful neuro-prosthetic devices which allows hearing restoration, several aspects still need to be improved. Interactions between stimulating electrodes through current spread occurring within the cochlea drastically limit the number of discriminable frequency channels and thus can ultimately result in poor speech perception. One potential solution relies on the use of new pulse shapes, such as asymmetric pulses, which can potentially reduce the current spread within the cochlea. The present study characterized the impact of changing electrical pulse shapes from the standard biphasic symmetric to the asymmetrical shape by quantifying the evoked firing rate and the spatial activation in the guinea pig primary auditory cortex (A1). At a fixed charge, the firing rate and the spatial activation in A1 decreased by 15 to 25 % when asymmetric pulses were used to activate the auditory nerve fibers, suggesting a potential reduction of the spread of excitation inside the cochlea. A strong "polarity-order" effect was found as the reduction was more pronounced when the first phase of the pulse was cathodic with high amplitude. These results suggest that the use of asymmetrical pulse shapes in clinical settings can potentially reduce the channel interactions in CI users.

Boosted selective internal radiation therapy with 90Y-loaded glass microspheres (B-SIRT) for hepatocellular carcinoma patients: a new personalized promising concept.

PURPOSE: To evaluate the impact of dosimetry based on MAA SPECT/CT for the prediction of response, toxicity and survival, and for treatment planning in patients with hepatocellular carcinoma (HCC) treated with (90)Y-loaded glass microspheres (TheraSphere®). METHODS: TheraSphere® was administered to 71 patients with inoperable HCC. MAA SPECT/CT quantitative analysis was used for the calculation of the tumour dose (TD), healthy injected liver dose (HILD), and total injected liver dose. Response was evaluated at 3 months using EASL criteria. Time to progression (TTP) and overall survival (OS) were evaluated using the Kaplan-Meier method. Factors potentially associated with liver toxicity were combined to construct a liver toxicity score (LTS). RESULTS: The response rate was 78.8%. Median TD were 342 Gy for responding lesions and 191 Gy for nonresponding lesions (p < 0.001). With a threshold TD of 205 Gy, MAA SPECT/CT predicted response with a sensitivity of 100% and overall accuracy of 90%. Based on TD and HILD, 17 patients underwent treatment intensification resulting in a good response rate (76.4%), without increased grade III liver toxicity. The median TTP and OS were 5.5 months (2-9.5 months) and 11.5 months (2-31 months), respectively, in patients with TD <205 Gy and 13 months (10-16 months) and 23.2 months (17.5-28.5 months), respectively, in those with TD >205 Gy (p = 0.0015 and not significant). Among patients with portal vein thrombosis (PVT) (n = 33), the median TTP and OS were 4.5 months (2-7 months) and 5 months (2-8 months), respectively, in patients with TD <205 Gy and 10 months (6-15.2 months) and 21.5 months (12-28.5 months), respectively, in those with TD >205 Gy (p = 0.039 and 0.005). The median OS was 24.5 months (18-28.5 months) in PVT patients with TD >205 Gy and good PVT targeting on MAA SPECT/CT. The LTS was able to detect severe liver toxicity (n = 6) with a sensitivity of 83% and overall accuracy of 97%. CONCLUSION: Dosimetry based on MAA SPECT/CT was able to accurately predict response and survival in patients treated with glass microspheres. This method can be used to adapt the injected activity without increasing liver toxicity, thus defining a new concept of boosted selective internal radiation therapy (B-SIRT). This new concept and LTS enable fully personalized treatment planning with glass microspheres to be achieved.

Drug-drug interactions with proton pump inhibitors in cancer patients: an underrecognized cause of treatment failure.

New concepts and drugs have revolutionized medical treatment for cancers. These drugs, which are very expensive and usually well tolerated, have dramatically improved cancer prognosis. We must use them wisely for patients to fully benefit. Gastric acid antisecretory drugs and particularly proton pump inhibitors (PPIs) revolutionized the treatment of gastroduodenal ulcers and severe gastroesophageal reflux, but are frequently overused for symptomatic treatment of epigastric pain or heartburn. Long-term acid suppression may alter the efficacy of many anticancer drugs, such as tyrosine kinase inhibitors (TKIs), cyclin-dependent kinase (CDK) 4/6 inhibitors and immune checkpoint inhibitors (ICIs), by either decreasing gastric acid secretion and thus drug absorption, or by modifying the gut microbiome that modulates the response to ICIs. Oncologists thus need to pay particular attention to the concomitant use of PPIs and anticancer drugs. These interactions translate into major clinical impacts, with demonstrated loss of efficacy for some TKIs (erlotinib, gefitinib, pazopanib), and conflicting results with many other oral drugs, including capecitabine and CDK 4/6 inhibitors. Furthermore, the profound changes in the gut microbiome due to using PPIs have shown that the benefit of using ICIs may be suppressed in patients treated with PPIs. As the use of PPIs is not essential, we must apply the precautionary principle. The first sentence of a recent Comment in Nature was "Every day, millions of people are taking medications that will not help them". We fear that every day millions of cancer patients are taking medications that harm them. While this may well be only association and not causation, there is enough to make us pause until we reach a clear answer. All these data should encourage medical oncologists to refrain from prescribing PPIs, explaining to patients the risks of interaction in order to prevent inappropriate prescription by another physician.

How I treat biliary tract cancer.

Management of biliary tract cancers (BTCs) is rapidly evolving. Curative management relies on surgical resection followed by adjuvant capecitabine for cholangiocarcinoma and gallbladder cancers. Unfortunately relapse rate remains high, and better adjuvant strategies are urgently required. A majority of patients are diagnosed with advanced disease, when chemotherapy with cisplatin and gemcitabine followed by second-line 5-FU and oxaliplatin /irinotecan is the cornerstone of treatment for most patients in the absence of targetable alterations. Targeted therapies, including therapies for tumours with fibroblast growth factor receptor-2 (FGFR-2) fusions, isocitrate dehydrogenase-1 (IDH-1) mutations, B-Raf proto-oncogene serine/threonine kinase (BRAF) V600E mutations, neurotrophic tyrosine receptor kinase (NTRK) fusions, Human epidermal growth factor-2 (HER-2) amplifications, and/or microsatellite instability are rapidly changing the treatment paradigm for many patients with advanced BTC, especially for patients with intrahepatic cholangiocarcinoma. Because of this, molecular profiling should be considered early on patients pathway to allow adequate planning of therapy. Ongoing research is likely to clarify the role of immunotherapy, liver-directed therapy, and liver transplant for BTCs in the future.

[The neutrophil gelatinase-associated lipocalin, or LCN 2, marker of aggressiveness in clear cell renal cell carcinoma]. / La neutrophil gelatinase-associated lipocalin, ou LCN 2, facteur d'agressivité dans le carcinome rénal à cellules claires (CRCC).

OBJECTIVE: To determine the prognostic significance of the neutrophil gelatinase-associated lipocalin (NGAL) and the matrix metalloproteinase 9 (MMP-9) in clear cell renal cell carcinoma (CCRCC). PATIENTS AND METHODS: NGAL and MMP-9 expression were quantified by immunohistochemistry in clear renal cell carcinoma tissues and in sera by Enzyme Linked Immunosorbent Assay (Elisa). Results were associated with clinicopathologic data. RESULTS: Seventy-four patients operated for CCRCC in Rennes between 2003 and 2009 were included. High concentrations of NGAL-MMP-9 complex in serum were associated with short progression free survival (PFS) (33.3 months versus 47.3 months, P=0.016) and poor overall survival (42.5 months versus 51.9 months, P<0.047). High NGAL concentrations in serum were also associated with shorter PFS (13.6 months versus 41.6 months, P=0.04). However, no NGAL expression was observed in renal tumor cells. Interestingly, NGAL was expressed by neutrophils infiltrating CCRCC and we showed that the density of NGAL expressing neutrophils was associated with pejorative PFS and survival (36.9months versus 56.1 months, P<0.006). CONCLUSION: In this study, we showed the pejorative significance of NGAL-MMP-9 complex and NGAL rates in serum of CCRCC. We also confirmed that density of NGAL expressing neutrophils in CCRCC was associated with poor outcome.

Robustness to Noise in the Auditory System: A Distributed and Predictable Property.

Background noise strongly penalizes auditory perception of speech in humans or vocalizations in animals. Despite this, auditory neurons are still able to detect communications sounds against considerable levels of background noise. We collected neuronal recordings in cochlear nucleus (CN), inferior colliculus (IC), auditory thalamus, and primary and secondary auditory cortex in response to vocalizations presented either against a stationary or a chorus noise in anesthetized guinea pigs at three signal-to-noise ratios (SNRs; -10, 0, and 10 dB). We provide evidence that, at each level of the auditory system, five behaviors in noise exist within a continuum, from neurons with high-fidelity representations of the signal, mostly found in IC and thalamus, to neurons with high-fidelity representations of the noise, mostly found in CN for the stationary noise and in similar proportions in each structure for the chorus noise. The two cortical areas displayed fewer robust responses than the IC and thalamus. Furthermore, between 21% and 72% of the neurons (depending on the structure) switch categories from one background noise to another, even if the initial assignment of these neurons to a category was confirmed by a severe bootstrap procedure. Importantly, supervised learning pointed out that assigning a recording to one of the five categories can be predicted up to a maximum of 70% based on both the response to signal alone and noise alone.

Trifluridine/tipiracil in combination with oxaliplatin and either bevacizumab or nivolumab in metastatic colorectal cancer: a dose-expansion, phase I study.

BACKGROUND: In preclinical studies trifluridine/tipiracil (FTD/TPI) plus oxaliplatin (Industriestrasse, Holzkirchen, Germany) sensitised microsatellite stable (MSS) metastatic colorectal cancer (mCRC) to anti-programmed cell death protein-1; the addition of oxaliplatin or bevacizumab (F Hoffmann- la ROCHE AG, Kaiseraugst, Switzerland) enhanced the antitumour effects of FTD/TPI. This study aimed to investigate the safety and efficacy of FTD/TPI plus oxaliplatin and either bevacizumab or nivolumab (Uxbridge business Park, Uxbridge, United Kingdom) in patients with mCRC who had progressed after at least one prior line of treatment. PATIENTS AND METHODS: In 14-day cycles, patients received FTD/TPI 35 mg/m2 (twice daily, days 1-5) plus oxaliplatin 85 mg/m2 (day 1), and, on day 1, either bevacizumab 5 mg/kg (cohort A) or nivolumab 3 mg/kg (cohort B). Patients in Cohort B had confirmed MSS status. RESULTS: In total, 54 patients were enrolled: 37 in cohort A and 17 in cohort B. Recruitment in cohort B was stopped early due to the low response rate (RR) observed at interim analyses of efficacy. The most common adverse events (AEs) in cohort A were neutropenia/decreased neutrophils (75.7%), nausea (59.5%), vomiting (40.5%), diarrhoea (37.8%), peripheral sensory neuropathy (37.8%), fatigue (35.1%) and decreased appetite (35.1%). In cohort B, the most common AEs were neutropenia/decreased neutrophils (70.6%), diarrhoea (58.8%), nausea (47.1%), vomiting (47.1%), fatigue (47.1%), asthenia (41.2%), paraesthesia (41.2%), thrombocytopenia/decreased platelets (35.3%) and decreased appetite (35.3%). Confirmed objective RR was 17.1% in cohort A and 7.1% in cohort B; the corresponding values for median progression-free survival in the two cohorts were 6.3 and 6.0 months. CONCLUSION: FTD/TPI plus oxaliplatin and bevacizumab or nivolumab had an acceptable safety profile and demonstrated antitumour activity in previously treated patients with mCRC.

Angiotensin-2 receptors (AT1-R and AT2-R), new prognostic factors for renal clear-cell carcinoma?

BACKGROUND: The growth factor Angiotensin-2 signals through Angiotensin receptor type 1 (AT1-R) in a broad range of cell types and tumours and through the type-2 receptor (AT2-R) in a more restricted group of cell types. Although numerous forms of cancer have been shown to overexpress AT1-R, expression of AT1-R and AT2-R by human renal clear-cell carcinoma (RCCC) is not well understood. In this study, the expression of both angiotensin receptors was quantified in a retrospective series of RCCC and correlated with prognostic factors. METHODS: Angiotensin receptor type 1 and AT2-R expressions were quantified on tumour tissues by immunohistochemistry (IHC), western blot and quantitative reverse transcriptase PCR (qRT-PCR). IHC results were correlated to Fuhrman's grade and patient progression-free survival (PFS). RESULTS: A total of 84 RCCC were analysed. By IHC, AT1-R and AT2-R were expressed to a greater level in high-grade tumours (AT1-R: P<0.001, AT2-R: P<0.001). Univariate analysis showed a correlation between PFS and AT1-R or AT2-R expression (P=0.001). By multivariate analysis, only AT2-R expression correlated with PFS (HR 1.021, P=0.006) and cancer stage (P<0.001). By western blot, AT1-R and AT1-R were also found to be overexpressed in higher Fuhrman's grade (P<0.01 and P=0.001 respectively). By qRT-PCR, AT1-R but not AT2-R mRNA were downregulated (P=0.001 and P=0.118, respectively). CONCLUSION: Our results show that AT1-R and AT2-R proteins are overexpressed in the most aggressive forms of RCCC and that AT2-R expression correlates with PFS. AT1-R or AT2-R blockage could, therefore, offer novel directions for anti-RCCC therapy.

Loss of SMARCB1 expression in colon carcinoma.

SMARCB1 is a tumor suppressor gene, which is part of SWI/SNF complex involved in transcriptional regulation. Recently, loss of SMARCB1 expression has been reported in gastrointestinal carcinomas. Our purpose was to evaluate the incidence and prognostic value of SMARCB1 loss in colon carcinoma (CC). Patients with stage III CC (n= 1695), and a second cohort of 23 patients with poorly differentiated CC were analyzed. Immunohistochemistry for SMARCB1 was performed on tissue microarrays, and cases with loss of expression were controlled on whole sections. Loss of SMARCB1 was compared with the clinico-pathological and molecular characteristics, and the prognostic value was evaluated. Loss of SMARCB1 was identified in 12 of 1695 (0.7%) patients with stage III CC. Whole section controls showed a complete loss in only one of these cases, corresponding to a medullary carcinoma. SMARCB1 loss was not associated with histological grade, tumor size nor survival. In the cohort of poorly differentiated CC, we detected 2/23 (8.7%) cases with loss of SMARCB1; one was rhabdoid while the other had medullary and mucinous histology. These 2 cases were deficient for MisMatched Repair (dMMR) and mutated for BRAF. SMARCB1 loss is rare in stage III CC, but appears more frequent in poorly differentiated CC.

Age-related Changes in Auditory Cortex Without Detectable Peripheral Alterations: A Multi-level Study in Sprague-Dawley Rats.

Aging is often considered to affect both the peripheral (i.e. the cochlea) and central (brainstem and thalamus-cortex) auditory systems. We investigated the effects of aging on the cochlea, brainstem and cortex of female Sprague-Dawley rats. The auditory nerve threshold remained stable between the ages of nine and 21 months, as did distortion product otoacoustic emissions and the number of ribbon synapses between inner hair cells and nerve fibers. The first clear signs of aging appeared in the brainstem, in which response amplitude decreased, with thresholds remaining stable until the age of 15 months, and increasing slightly thereafter. The responses of primary auditory cortex neurons revealed specific effects of aging: at 21 months, receptive fields were spectrally narrower and the temporal reliability of responses to communication sounds was lower. However, aging had a null or even positive effect on neuronal responses in the presence of background noise, responses to amplitude-modulated sounds, and responses in gap-detection protocols. Overall, inter-animal variability remained high relative to the variability across groups of different ages, for all parameters tested. Behavioral performance for the modulation depth of amplitude modulation noise was worse in 21-month old animals than in other animals. Age-related alterations of cortical and behavioral responses were thus observed in animals displaying no signs of aging at the peripheral level. These results suggest that intrinsic, central aging effects can affect the perception of acoustic stimuli independently of the effects of aging on peripheral receptors.

Transarterial Radioembolization (TARE) Agents beyond 90Y-Microspheres.

Liver malignancies, either primary tumours (mainly hepatocellular carcinoma and cholangiocarcinoma) or secondary hepatic metastases, are a major cause of death, with an increasing incidence. Among them, hepatocellular carcinoma (HCC) presents with a dark prognosis because of underlying liver diseases and an often late diagnosis. A curative surgical treatment can therefore only be proposed in 20 to 30% of the patients. However, new treatment options for intermediate to advanced stages, such as internal radionuclide therapy, seem particularly attractive. Transarterial radioembolization (TARE), which consists in the use of intra-arterial injection of a radiolabelled embolising agent, has led to very promising results. TARE with 90Y-loaded microspheres is now becoming an established procedure to treat liver tumours, with two commercially available products (namely, SIR-Sphere® and TheraSphere®). However, this technology remains expensive and is thus not available everywhere. The aim of this review is to describe TARE alternative technologies currently developed and investigated in clinical trials, with special emphasis on HCC.

Prognostic scores for sorafenib-treated hepatocellular carcinoma patients: A new application for the hepatoma arterial embolisation prognostic score.

BACKGROUND: No prognostic classification is currently used for patients treated with systemic therapies for Hepatocellular Carcinoma (HCC). METHODS: We retrospectively analysed data from patients treated with sorafenib for HCC from five centres in France and in the United Kingdom (UK). The training set comprised data from two centres and the validation set from three. Variables independently associated with Overall Survival (OS) in the training set were used to build the SAP (Sorafenib Advanced HCC Prognosis) score. The score was tested in the validation set, then compared with other prognostication systems. RESULTS: The training set and validation set included 370 and 468 patients respectively. In the training set, variables independently associated with OS in multivariable analysis were: performance status (PS) >0, alpha-fetoprotein (AFP) >400 ng/ml, tumour size >7 cm, bilirubin >17 µmol/l and albumin <36 g/l. The SAP score was built giving one point to each abnormal variable, and three classes were constructed. The SAP score was significantly associated with OS in the training set, with median OS of 14.9 months for SAP A, 7.2 months for SAP B and 2.5 months for SAP C (P < 0.001). In the validation set, the SAP score was significantly associated with OS, and showed greater discriminative abilities than Barcelona Clinic Liver Cancer (BCLC) and albumin-bilirubin (ALBI) scores. However, the hepatoma arterial embolisation prognostic (HAP) score showed greater discriminative abilities than the SAP score. CONCLUSION: In European patients treated with sorafenib, the HAP was the most discriminant prognostic score and may facilitate stratification in trials and inform clinical decision making.

Learning-induced physiological plasticity in the thalamo-cortical sensory systems: a critical evaluation of receptive field plasticity, map changes and their potential mechanisms.

The goal of this review is to give a detailed description of the main results obtained in the field of learning-induced plasticity. The review is focused on receptive field and map changes observed in the auditory, somatosensory and visual thalamo-cortical system as a result of an associative training performed in waking animals. Receptive field (RF) plasticity, 2DG and map changes obtained in the auditory and somatosensory system are reviewed. In the visual system, as there is no RF and map analysis during learning per se, the evidence presented are from increased neuronal responsiveness, and from the effects of perceptual learning in human and non human primates. Across sensory modalities, the re-tuning of neurons to a significant stimulus or map reorganizations in favour of the significant stimuli were observed at the thalamic and/or cortical level. The analysis of the literature in each sensory modality indicates that relationships between learning-induced sensory plasticity and behavioural performance can, or cannot, be found depending on the tasks that were used. The involvement (i) of Hebbian synaptic plasticity in the described neuronal changes and (ii) of neuromodulators as "gating" factors of the neuronal changes, is evaluated. The weakness of the Hebbian schema to explain learning-induced changes and the need to better define what the word "learning" means are stressed. It is suggested that future research should focus on the dynamic of information processing in sensory systems, and the concept of "effective connectivity" should be useful in that matter.

Auditory thalamus responses to guinea-pig vocalizations: a comparison between rat and guinea-pig.

Although neuronal responses to species-specific vocalizations have long been described, very few between-species comparisons have been made. In a previous study, a differential representation of species-specific vocalizations was found in the auditory cortex (ACx): marmoset ACx neurons responded more, and more selectively, to marmoset calls than did cat ACx neurons [Wang, X., Kadia, S.C., 2001. Differential representation of species-specific primate vocalizations in the auditory cortices of marmoset and cat. J. Neurophysiol. 86, 2616-2620]. The present study analyzed responses of guinea-pig and rat auditory thalamus neurons to four well-defined guinea-pig vocalizations. Neurons of guinea-pigs (n = 96) and rats (n = 87) displayed similar response strength to guinea-pig vocalizations, and did not exhibit a preference for the natural over the time-reversed version of the calls in both species. This difference with the study by Wang and Kadia might suggest that, in mammals, the selectivity for the natural version of species-specific vocalizations is prominent only at the cortical level.