jquery - "TypeError: Cannot read property 'setState' of undefined" when reading JSON into state

I know this question has been asked before, but I've tried all the suggested solutions and none of them work (which might, admittedly, be down to me being a numpty).

Anywho, my particular problem is that the following line is causing the error ('TypeError: Cannot read property 'setState' of undefined'): this.setState({pictures : response, loading: false});

FWIW, the previous line is a console.log call that tells me that the response has come back OK.

Here's the code in its entirety:

import {Component} from 'react'
import fetch from 'isomorphic-fetch'

import {Checkbox, CheckboxGroup} from 'react-checkbox-group';
import Thumbs from './Thumbs';

class Search extends Component {

constructor(props) {
    super(props)
    this.state = {
        loading: false,
        images: false,

        audio: false,
        pictures: []
    }
    this.handleSubmit = this.handleSubmit.bind(this);
}

componentWillUpdate(nextProps) {
    this.style = {backgroundColor: 'green'}
}


handleSubmit(e) {
    e.preventDefault();
    const search = e.target[0].value;
    const vid = e.target[1].checked;
    const aud = e.target[2].checked;

    var medium = "image";

    if (aud) {
        medium = "audio";

    }

    var endPoint = "https://images-api.nasa.gov/search?q=" + search + "&media_type=" + medium;
    console.log(endPoint);
    fetch(endPoint)
        .then(function(response) {
            if (response.status >= 400) {
                throw new Error("Bad response from server");
            }
            return response.json();

        })
        .then(function(response) {
            console.log(response);
            this.setState({pictures : response, loading: false});                //PROBLEM IS HERE
        });

}


render() {

    const { pictures, loading } = this.state
    function mediaChanged(newMedia) {
        if (newMedia.length === 2) {
            newMedia.shift();
        }
    };

    return (
        

            
NASA Search

            

                

                                    name="media"
                    onChange={mediaChanged}>
                     Images
                     Audio
                
            
            






            {(pictures.length) ?
                pictures.map(
                    (pictures, i) =>
                        
                ) :
                -
            }
        
    )
}

}

export default Search