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Mandeville JB, Levine MA, Arsenault JT, Vanduffel W, Rosen BR, Sander CY. A reference tissue forward model for improved PET accuracy using within-scan displacement studies. J Cereb Blood Flow Metab 2022; 42:1007-1019. [PMID: 34894821 PMCID: PMC9125481 DOI: 10.1177/0271678x211065212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 10/22/2021] [Accepted: 11/07/2021] [Indexed: 12/13/2022]
Abstract
We report a novel forward-model implementation of the full reference tissue model (fFTRM) that addresses the fast-exchange approximation employed by the simplified reference tissue model (SRTM) by incorporating a non-zero dissociation time constant from the specifically bound compartment. The forward computational approach avoided errors associated with noisy and nonorthogonal basis functions using an inverse linear model. Compared to analysis by a multilinear single-compartment reference tissue model (MRTM), fFTRM provided improved accuracy for estimation of binding potentials at early times in the scan, with no worse reproducibility across sessions. To test the model's ability to identify small focal changes in binding potential using a within-scan challenge, we employed a nonhuman primate model of focal dopamine release elicited by deep brain microstimulation remote to ventral striatum (VST) during imaging by simultaneous PET and fMRI. The new model reported an unambiguously lateralized response in VST consistent with fMRI, whereas the MRTM-derived response was not lateralized and was consistent with simulations of model bias. The proposed model enabled better accuracy in PET [11C]raclopride displacement studies and may also facilitate challenges sooner after injection, thereby recovering some sensitivity lost to radioactive decay of the PET tracer.
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Affiliation(s)
- Joseph B Mandeville
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Massachusetts General Hospital, Boston, MA, USA
- Harvard Medical School, Boston, MA, USA
| | - Michael A Levine
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Massachusetts General Hospital, Boston, MA, USA
- Harvard Medical School, Boston, MA, USA
| | - John T Arsenault
- Laboratory for Neuro- and Psychophysiology, KU Leuven, Leuven, Belgium
| | - Wim Vanduffel
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Massachusetts General Hospital, Boston, MA, USA
- Harvard Medical School, Boston, MA, USA
- Laboratory for Neuro- and Psychophysiology, KU Leuven, Leuven, Belgium
| | - Bruce R Rosen
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Massachusetts General Hospital, Boston, MA, USA
- Harvard Medical School, Boston, MA, USA
| | - Christin Y Sander
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Massachusetts General Hospital, Boston, MA, USA
- Harvard Medical School, Boston, MA, USA
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Herpers J, Arsenault JT, Vanduffel W, Vogels R. Stimulation of the ventral tegmental area induces visual cortical plasticity at the neuronal level. Cell Rep 2021; 37:109998. [PMID: 34758325 DOI: 10.1016/j.celrep.2021.109998] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 09/20/2021] [Accepted: 10/22/2021] [Indexed: 11/17/2022] Open
Abstract
fMRI studies have shown that pairing a task-irrelevant visual feature with electrical micro-stimulation of the ventral tegmental area (VTA-EM) is sufficient to increase the sensory cortical representation of the paired feature and to improve perceptual performance. However, since fMRI provides an indirect measure of neural activity, the neural response changes underlying the fMRI activations are unknown. Here, we pair a task-irrelevant grating orientation with VTA-EM while attention is directed to a difficult orthogonal task. We examine the changes in neural response properties in macaques by recording spiking activity in the posterior inferior temporal cortex, the locus of fMRI-defined plasticity in previous studies. We observe a relative increase in mean spike rate and preference for the VTA-EM paired orientation compared to an unpaired orientation, which is unrelated to attention. These results demonstrate that VTA-EM-stimulus pairing is sufficient to induce sensory cortical plasticity at the spiking level in nonhuman primates.
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Affiliation(s)
- Jerome Herpers
- Laboratory for Neuro- and Psychophysiology, Department of Neurosciences, KU Leuven Medical School, 3000 Leuven, Belgium; Leuven Brain Institute, KU Leuven, 3000 Leuven, Belgium
| | - John T Arsenault
- Laboratory for Neuro- and Psychophysiology, Department of Neurosciences, KU Leuven Medical School, 3000 Leuven, Belgium; Leuven Brain Institute, KU Leuven, 3000 Leuven, Belgium
| | - Wim Vanduffel
- Laboratory for Neuro- and Psychophysiology, Department of Neurosciences, KU Leuven Medical School, 3000 Leuven, Belgium; Leuven Brain Institute, KU Leuven, 3000 Leuven, Belgium; Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, USA; Department of Radiology, Harvard Medical School, Boston, MA 02144, USA
| | - Rufin Vogels
- Laboratory for Neuro- and Psychophysiology, Department of Neurosciences, KU Leuven Medical School, 3000 Leuven, Belgium; Leuven Brain Institute, KU Leuven, 3000 Leuven, Belgium.
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Vancraeyenest P, Arsenault JT, Li X, Zhu Q, Kobayashi K, Isa K, Isa T, Vanduffel W. Selective Mesoaccumbal Pathway Inactivation Affects Motivation but Not Reinforcement-Based Learning in Macaques. Neuron 2020; 108:568-581.e6. [DOI: 10.1016/j.neuron.2020.07.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Revised: 06/18/2020] [Accepted: 07/12/2020] [Indexed: 12/18/2022]
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Murris SR, Arsenault JT, Vanduffel W. Frequency- and State-Dependent Network Effects of Electrical Stimulation Targeting the Ventral Tegmental Area in Macaques. Cereb Cortex 2020; 30:4281-4296. [PMID: 32279076 PMCID: PMC7325806 DOI: 10.1093/cercor/bhaa007] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 01/06/2020] [Accepted: 01/08/2020] [Indexed: 01/03/2023] Open
Abstract
The ventral tegmental area (VTA) is a midbrain structure at the heart of the dopaminergic system underlying adaptive behavior. Endogenous firing rates of dopamine cells in the VTA vary from fast phasic bursts to slow tonic activity. Artificial perturbations of the VTA, through electrical or optogenetic stimulation methods, generate different and sometimes even contrasting behavioral outcomes depending on stimulation parameters such as frequency, amplitude, and pulse width. Here, we investigate the global functional effects of electrical stimulation frequency (10, 20, 50, and 100 Hz) of the VTA in rhesus monkeys. We stimulated 2 animals with chronic electrodes, either awake or anesthetized, while concurrently acquiring whole-brain functional magnetic resonance imaging (fMRI) signals. In the awake state, activity as a function of stimulation frequency followed an inverted U-shape in many cortical and subcortical structures, with highest activity observed at 20 and 50 Hz and lower activity at 10 and 100 Hz. Under anesthesia, the hemodynamic responses in connected brain areas were slightly positive at 10 Hz stimulation, but decreased linearly as a function of higher stimulation frequencies. A speculative explanation for the remarkable frequency dependence of stimulation-induced fMRI activity is that the VTA makes use of different frequency channels to communicate with different postsynaptic sites.
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Affiliation(s)
- Sjoerd R Murris
- Department of Neurosciences, Laboratory of Neuro- and Psychophysiology, KU Leuven Medical School, Leuven 3000, Belgium.,Leuven Brain Institute, KU Leuven, Leuven 3000, Belgium
| | - John T Arsenault
- Department of Neurosciences, Laboratory of Neuro- and Psychophysiology, KU Leuven Medical School, Leuven 3000, Belgium.,Leuven Brain Institute, KU Leuven, Leuven 3000, Belgium
| | - Wim Vanduffel
- Department of Neurosciences, Laboratory of Neuro- and Psychophysiology, KU Leuven Medical School, Leuven 3000, Belgium.,Leuven Brain Institute, KU Leuven, Leuven 3000, Belgium.,Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, USA.,Department of Radiology, Harvard Medical School, Boston, MA 02144, USA
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Caspari N, Arsenault JT, Vandenberghe R, Vanduffel W. Functional Similarity of Medial Superior Parietal Areas for Shift-Selective Attention Signals in Humans and Monkeys. Cereb Cortex 2019; 28:2085-2099. [PMID: 28472289 DOI: 10.1093/cercor/bhx114] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Indexed: 11/14/2022] Open
Abstract
We continually shift our attention between items in the visual environment. These attention shifts are usually based on task relevance (top-down) or the saliency of a sudden, unexpected stimulus (bottom-up), and are typically followed by goal-directed actions. It could be argued that any species that can covertly shift its focus of attention will rely on similar, evolutionarily conserved neural substrates for processing such shift-signals. To address this possibility, we performed comparative fMRI experiments in humans and monkeys, combining traditional, and novel, data-driven analytical approaches. Specifically, we examined correspondences between monkey and human brain areas activated during covert attention shifts. When "shift" events were compared with "stay" events, the medial (superior) parietal lobe (mSPL) and inferior parietal lobes showed similar shift sensitivities across species, whereas frontal activations were stronger in monkeys. To identify, in a data-driven manner, monkey regions that corresponded with human shift-selective SPL, we used a novel interspecies beta-correlation strategy whereby task-related beta-values were correlated across voxels or regions-of-interest in the 2 species. Monkey medial parietal areas V6/V6A most consistently correlated with shift-selective human mSPL. Our results indicate that both species recruit corresponding, evolutionarily conserved regions within the medial superior parietal lobe for shifting spatial attention.
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Affiliation(s)
- Natalie Caspari
- Laboratory for Neuro- and Psychophysiology, Department of Neurosciences, KU Leuven Medical School, 3000 Leuven, Belgium.,Laboratory for Cognitive Neurology, Department of Neurosciences, KU Leuven, 3000 Leuven, Belgium
| | - John T Arsenault
- Laboratory for Neuro- and Psychophysiology, Department of Neurosciences, KU Leuven Medical School, 3000 Leuven, Belgium.,Massachusetts General Hospital, Martinos Center for Biomedical Imaging, Charlestown, MA 02129, USA
| | - Rik Vandenberghe
- Laboratory for Cognitive Neurology, Department of Neurosciences, KU Leuven, 3000 Leuven, Belgium.,University Hospitals Leuven, Department of Neurology, 3000 Leuven, Belgium
| | - Wim Vanduffel
- Laboratory for Neuro- and Psychophysiology, Department of Neurosciences, KU Leuven Medical School, 3000 Leuven, Belgium.,Massachusetts General Hospital, Martinos Center for Biomedical Imaging, Charlestown, MA 02129, USA.,Harvard Medical School, Department of Radiology, Boston, MA 02115, USA
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Li X, Zhu Q, Janssens T, Arsenault JT, Vanduffel W. In Vivo Identification of Thick, Thin, and Pale Stripes of Macaque Area V2 Using Submillimeter Resolution (f)MRI at 3 T. Cereb Cortex 2017; 29:544-560. [DOI: 10.1093/cercor/bhx337] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 11/29/2017] [Indexed: 11/14/2022] Open
Affiliation(s)
- Xiaolian Li
- Laboratory of Neuro- and Psychophysiology, Department of Neurosciences, KU Leuven Medical School, Leuven, Belgium
| | - Qi Zhu
- Laboratory of Neuro- and Psychophysiology, Department of Neurosciences, KU Leuven Medical School, Leuven, Belgium
| | - Thomas Janssens
- Laboratory of Neuro- and Psychophysiology, Department of Neurosciences, KU Leuven Medical School, Leuven, Belgium
- Current address: Siemens Healthcare Belgium, Beersel, Belgium
| | - John T Arsenault
- Laboratory of Neuro- and Psychophysiology, Department of Neurosciences, KU Leuven Medical School, Leuven, Belgium
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA
| | - Wim Vanduffel
- Laboratory of Neuro- and Psychophysiology, Department of Neurosciences, KU Leuven Medical School, Leuven, Belgium
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA
- Department of Radiology, Harvard Medical School, Boston, MA, USA
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Abstract
In this issue of Neuron, Lee et al. (2016) assessed the brain-wide effects of stimulating the direct and indirect pathway by optogenetic activation of D1 and D2 striatal neurons. This work demonstrates the exquisite power of combining cell-type-specific perturbation methods with focal and whole-brain measurements of brain activity.
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Affiliation(s)
- Wim Vanduffel
- Laboratory of Neuro-and Psychophysiology, Department of Neurosciences, KU Leuven Medical School, 3000 Leuven, Belgium; Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, USA; Department of Radiology, Harvard Medical School, Boston, MA 02114, USA.
| | - John T Arsenault
- Laboratory of Neuro-and Psychophysiology, Department of Neurosciences, KU Leuven Medical School, 3000 Leuven, Belgium; Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, USA
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Abstract
In this issue of Neuron, Kiani et al. (2015) show that the correlated activity of multiple simultaneously recorded neurons can be used to identify, in a completely un-biased manner, distinct functional domains within prefrontal and (pre)motor cortex of macaque monkeys.
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Affiliation(s)
- Wim Vanduffel
- Laboratory of Neuro- and Psychophysiology, Department of Neurosciences, KU Leuven Medical School, 3000 Leuven, Belgium; Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, USA; Department of Radiology, Harvard Medical School, Boston, MA 02144, USA.
| | - John T Arsenault
- Laboratory of Neuro- and Psychophysiology, Department of Neurosciences, KU Leuven Medical School, 3000 Leuven, Belgium; Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, USA
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Arsenault JT, Nelissen K, Jarraya B, Vanduffel W. Dopaminergic reward signals selectively decrease fMRI activity in primate visual cortex. Neuron 2013; 77:1174-86. [PMID: 23522051 DOI: 10.1016/j.neuron.2013.01.008] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/04/2013] [Indexed: 10/27/2022]
Abstract
Stimulus-reward coupling without attention can induce highly specific perceptual learning effects, suggesting that reward triggers selective plasticity within visual cortex. Additionally, dopamine-releasing events-temporally surrounding stimulus-reward associations-selectively enhance memory. These forms of plasticity may be evoked by selective modulation of stimulus representations during dopamine-inducing events. However, it remains to be shown whether dopaminergic signals can selectively modulate visual cortical activity. We measured fMRI activity in monkey visual cortex during reward-only trials apart from intermixed cue-reward trials. Reward without visual stimulation selectively decreased fMRI activity within the cue representations that had been paired with reward during other trials. Behavioral tests indicated that these same uncued reward trials strengthened cue-reward associations. Furthermore, such spatially-specific activity modulations depended on prediction error, as shown by manipulations of reward magnitude, cue-reward probability, cue-reward familiarity, and dopamine signaling. This cue-selective negative reward signal offers a mechanism for selectively gating sensory cortical plasticity.
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Affiliation(s)
- John T Arsenault
- Laboratory of Neuro and Psychophysiology, KU Leuven Medical School, Campus Gasthuisberg, 3000 Leuven, Belgium
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Nelissen K, Jarraya B, Arsenault JT, Rosen BR, Wald LL, Mandeville JB, Marota JJ, Vanduffel W. Neural correlates of the formation and retention of cocaine-induced stimulus-reward associations. Biol Psychiatry 2012; 72:422-8. [PMID: 22440616 DOI: 10.1016/j.biopsych.2012.02.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Revised: 01/27/2012] [Accepted: 02/19/2012] [Indexed: 10/28/2022]
Abstract
BACKGROUND Cocaine can elicit drug-seeking behavior for drug-predicting stimuli, even after a single stimulus-cocaine pairing. Although orbitofrontal cortex is thought to be important during encoding and maintenance of stimulus-reward value, we still lack a comprehensive model of the neural circuitry underlying this cognitive process. METHODS We studied the conditioned effects of cocaine with monkey functional magnetic resonance imaging and classical conditioning by pairing a visual shape (conditioning stimulus [CS+]) with a noncontingent cocaine infusion; a control stimulus was never paired. We correlated the behavioral preference of the monkey for the CS+, as measured offline, with the activity induced by the CS+ relative to the control stimulus as function of time. RESULTS We observed that during formation of stimulus-cocaine associations strong CS+-induced functional magnetic resonance imaging activations emerged in frontal cortex that correlated significantly with behavioral CS+ preference. Afterward, CS+ preference correlated only with activity in early visual cortex. Control experiments suggest that these findings cannot be explained by increased familiarity for the CS+. CONCLUSIONS Our findings suggest a complex interaction between frontal and occipital cortex during cocaine conditioning. Frontal cortex is important for establishing novel representations of stimulus valence when cocaine is used as reinforcer, whereas early visual cortex is involved in retaining these cocaine-stimulus associations.
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Affiliation(s)
- Koen Nelissen
- Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Boston, Massachusetts, USA.
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Janssens T, Keil B, Farivar R, McNab JA, Polimeni JR, Gerits A, Arsenault JT, Wald LL, Vanduffel W. An implanted 8-channel array coil for high-resolution macaque MRI at 3T. Neuroimage 2012; 62:1529-36. [PMID: 22609793 DOI: 10.1016/j.neuroimage.2012.05.028] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Accepted: 05/10/2012] [Indexed: 10/28/2022] Open
Abstract
An 8-channel receive coil array was constructed and implanted adjacent to the skull in a male rhesus monkey in order to improve the sensitivity of (functional) brain imaging. The permanent implant was part of an acrylic headpost assembly and only the coil element loop wires were implanted. The tuning, matching, and preamplifier circuitry was connected via a removable external assembly. Signal-to-noise ratio (SNR) and noise amplification for parallel imaging were compared to single-, 4-, and 8-channel external receive-only coils routinely used for macaque fMRI. In vivo measurements showed significantly improved SNR within the brain for the implanted versus the external coils. Within a region-of-interest covering the cerebral cortex, we observed a 5.4-, 3.6-fold, and 3.4-fold increase in SNR compared to the external single-, 4-, and 8-channel coils, respectively. In the center of the brain, the implanted array maintained a 2.4×, 2.5×, and 2.1× higher SNR, respectively compared to the external coils. The array performance was evaluated for anatomical, diffusion tensor and functional brain imaging. This study suggests that a stable implanted phased-array coil can be used in macaque MRI to substantially increase the spatial resolution for anatomical, diffusion tensor, and functional imaging.
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Affiliation(s)
- T Janssens
- A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, USA
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Abstract
The frontal eye field (FEF) is one of several cortical regions thought to modulate sensory inputs. Moreover, several hypotheses suggest that the FEF can only modulate early visual areas in the presence of a visual stimulus. To test for bottom-up gating of frontal signals, we microstimulated subregions in the FEF of two monkeys and measured the effects throughout the brain with functional magnetic resonance imaging. The activity of higher-order visual areas was strongly modulated by FEF stimulation, independent of visual stimulation. In contrast, FEF stimulation induced a topographically specific pattern of enhancement and suppression in early visual areas, but only in the presence of a visual stimulus. Modulation strength depended on stimulus contrast and on the presence of distractors. We conclude that bottom-up activation is needed to enable top-down modulation of early visual cortex and that stimulus saliency determines the strength of this modulation.
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Affiliation(s)
- Leeland B Ekstrom
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, USA
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Fairchild WL, Swansburg EO, Arsenault JT, Brown SB. Does an association between pesticide use and subsequent declines in catch of Atlantic salmon (Salmo salar) represent a case of endocrine disruption? Environ Health Perspect 1999; 107:349-57. [PMID: 10210690 PMCID: PMC1566411 DOI: 10.1289/ehp.99107349] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Historical aerial applications of the insecticide Matacil 1.8D provide an opportunity to look for potential effects of the endocrine disrupting compound 4-nonylphenol (4-NP) on Atlantic salmon (Salmo salar) populations. Matacil 1.8D contained the carbamate insecticide aminocarb, with 4-NP as primary solvent. Between 1975 and 1985 Matacil 1.8D was applied to forests in Atlantic Canada to control damage from the spruce budworm (Choristoneura fumiferana). After spraying, estimated concentrations of 4-NP in water fell within a range in which estrogenic effects might be anticipated. The spraying coincided with final stages of smolt development in salmon. Salmon catch data were evaluated considering effects on survival of the smolt stage. There was a significant negative relationship between the returns of salmon and the proportion of tributaries sprayed within the Restigouche River drainage basin in 1977. There was also a broader event of unusually heavy salmon smolt mortality in 1977, which contains a significant relationship indicating that where Matacil 1.8D spraying occurred, the smolt mortality increased. For 16 rivers exposed to spraying between 1973 and 1990, a significant proportion (p<0.005) of the lowest salmon catches coincided with Matacil 1.8D spraying. A decline coinciding with the use of Matacil 1.8D was also apparent in blueback herring (Alosa aestivalis) catches in New Brunswick. Because similar relationships were not evident for Matacil 1.8F or fenitrothion, neither of which were formulated with 4-NP, we hypothesize that the 4-NP in Matacil 1.8D was the causal agent. Concentrations of 4-NP described here are within current ranges encountered in industrial effluents and municipal sewage outfalls.
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Affiliation(s)
- W L Fairchild
- Gulf Fisheries Centre, Fisheries and Oceans Canada, Moncton, New Brunswick, E1C 9B6, Canada
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